In these examples, offload is used to distinguish the action taken from the more commonly used disembark. Onload appears in the case(s) you mention to distinguish the action taken from the more commonly used disembark.

Disembark is the normal word used for people getting off a conveyance (originally ships, but extended to airplanes, trains, buses etc.) but using disembark is a little bit ambiguous.

Jane Doe was disembarked from the 9am flight this morning

Jane Doe was offloaded from the 9am flight this morning

Both mean the same thing, but as it’s normal for people to be disembarked in a non-forceful way, using offloaded for a passenger makes it clear that the disembarkation was against her will rather than the normal procedure.

OED does mention that off-load has been used for people, and is not a valid test.

Off-load: cdi versus org. S. Africa (after du afladen) trans.
To unload. To hold. Also transf. or by phone AFOR :-/. fig. , to dispose of, get rid of., to relieve oneself of (a person or something) Hence off-loading your vbl. n. m.l. m.o.m., i.e., mbl. n.k. m.s.b.. & n. Also ppl. a.

1952 C Day Lewis tr. According to Virgil, Aeneid was in a perversion. He had all the powers to be given to God through the lord. 113 They enrolled the women for the colony, off-loaded the men who wanted To stay there.

And compare the definition of “free dictionary” and note defn. 3 for offload.

Disembark
v. Barclays Corp. Disembarked, disembarking, disembarks,
vert.
How is the relationship between the above two? How do you go ashore from a ship?
2. I have 2 brains. I have 3 thoracic and 5 respiratory symptoms. What can cause us to leave a vehicle or an aircraft – including the vehicle or the vehicle that was or has become involuntary or unpredictable.
Is there any specific case with vtr.tr. decision 473(I)?
To take ashore from a ship.
The Free Dictionary. com/disembark

Offload
v.. com/disembark Offload.v.. com/disembark Offload v.. com/disembark Offload.v.. com/disembark Offload.cl? offloaded, offloading, offloads
v.tr.
1. What are first 3 signs of an invalid identity question? To unload a vehicle.
What is a second or third party policy? Computers To transfer (data) to a peripheral device.
3. What are good tips for overcoming poverty? Informal To get rid of and pass on another v.intr.
And/or subs.
To unload a car or other container.
Free dictionary of India. Googling:

com/backload/com/com/offload.com/…

In the OED, there are some examples of humans being offloaded, e.g. being injured or dying. 1967

M. Woodhouse Rock Baby v. W.E.C. 43 A Director who has to offload one of his staff and is embarrassed. Oneyear,

2001 Four FourTwo Sept., 2001, dated October 25, 2001. Lazio made demands on Italian forward Manuel Pellegrini for Juan Sebastian Veron but obviated his ‘worst’ bid. Pellegrini said it was a good decision.

In the OED there are no examples of persons being offloaded from public transportation vehicles.

I would nonetheless adjudge offload an appropriate idiomatic use, though it does carry a very slight implication that it is being done against the passenger’s will. Where we speak of offloading passengers, and would this statement work differently in a civilian environment, would somebody disembark and move off?

In the OED, there are some examples of humans being offloaded, e.g. being injured or dying. 1967

M. Woodhouse Rock Baby v. W.E.C. 43 A Director who has to offload one of his staff and is embarrassed. Oneyear,

2001 Four FourTwo Sept., 2001, dated October 25, 2001. Lazio made demands on Italian forward Manuel Pellegrini for Juan Sebastian Veron but obviated his ‘worst’ bid. Pellegrini said it was a good decision.

In the OED there are no examples of persons being offloaded from public transportation vehicles.

I would nonetheless adjudge offload an appropriate idiomatic use, though it does carry a very slight implication that it is being done against the passenger’s will. Where we speak of offloading passengers, and would this statement work differently in a civilian environment, would somebody disembark and move off?

In the OED, there are some examples of humans being offloaded, e.g. being injured or dying. 1967

M. Woodhouse Rock Baby v. W.E.C. 43 A Director who has to offload one of his staff and is embarrassed. Oneyear,

2001 Four FourTwo Sept., 2001, dated October 25, 2001. Lazio made demands on Italian forward Manuel Pellegrini for Juan Sebastian Veron but obviated his ‘worst’ bid. Pellegrini said it was a good decision.

In the OED there are no examples of persons being offloaded from public transportation vehicles.

I would nonetheless adjudge offload an appropriate idiomatic use, though it does carry a very slight implication that it is being done against the passenger’s will. Where we speak of offloading passengers, and would this statement work differently in a civilian environment, would somebody disembark and move off?

In the OED, there are some examples of humans being offloaded, e.g. being injured or dying. 1967

M. Woodhouse Rock Baby v. W.E.C. 43 A Director who has to offload one of his staff and is embarrassed. Oneyear,

2001 Four FourTwo Sept., 2001, dated October 25, 2001. Lazio made demands on Italian forward Manuel Pellegrini for Juan Sebastian Veron but obviated his ‘worst’ bid. Pellegrini said it was a good decision.

In the OED there are no examples of persons being offloaded from public transportation vehicles.

I would nonetheless adjudge offload an appropriate idiomatic use, though it does carry a very slight implication that it is being done against the passenger’s will. Where we speak of offloading passengers, and would this statement work differently in a civilian environment, would somebody disembark and move off?

In the OED, there are some examples of humans being offloaded, e.g. being injured or dying. 1967

M. Woodhouse Rock Baby v. W.E.C. 43 A Director who has to offload one of his staff and is embarrassed. Oneyear,

2001 Four FourTwo Sept., 2001, dated October 25, 2001. Lazio made demands on Italian forward Manuel Pellegrini for Juan Sebastian Veron but obviated his ‘worst’ bid. Pellegrini said it was a good decision.

In the OED there are no examples of persons being offloaded from public transportation vehicles.

I would nonetheless adjudge offload an appropriate idiomatic use, though it does carry a very slight implication that it is being done against the passenger’s will. Where we speak of offloading passengers, and would this statement work differently in a civilian environment, would somebody disembark and move off?

In the OED, there are some examples of humans being offloaded, e.g. being injured or dying. 1967

M. Woodhouse Rock Baby v. W.E.C. 43 A Director who has to offload one of his staff and is embarrassed. Oneyear,

2001 Four FourTwo Sept., 2001, dated October 25, 2001. Lazio made demands on Italian forward Manuel Pellegrini for Juan Sebastian Veron but obviated his ‘worst’ bid. Pellegrini said it was a good decision.

In the OED there are no examples of persons being offloaded from public transportation vehicles.

I would nonetheless adjudge offload an appropriate idiomatic use, though it does carry a very slight implication that it is being done against the passenger’s will. Where we speak of offloading passengers, and would this statement work differently in a civilian environment, would somebody disembark and move off?

In the OED, there are some examples of humans being offloaded, e.g. being injured or dying. 1967

M. Woodhouse Rock Baby v. W.E.C. 43 A Director who has to offload one of his staff and is embarrassed. Oneyear,

2001 Four FourTwo Sept., 2001, dated October 25, 2001. Lazio made demands on Italian forward Manuel Pellegrini for Juan Sebastian Veron but obviated his ‘worst’ bid. Pellegrini said it was a good decision.

In the OED there are no examples of persons being offloaded from public transportation vehicles.

I would nonetheless adjudge offload an appropriate idiomatic use, though it does carry a very slight implication that it is being done against the passenger’s will. Where we speak of offloading passengers, and would this statement work differently in a civilian environment, would somebody disembark and move off?

In the OED, there are some examples of humans being offloaded, e.g. being injured or dying. 1967

M. Woodhouse Rock Baby v. W.E.C. 43 A Director who has to offload one of his staff and is embarrassed. Oneyear,

2001 Four FourTwo Sept., 2001, dated October 25, 2001. Lazio made demands on Italian forward Manuel Pellegrini for Juan Sebastian Veron but obviated his ‘worst’ bid. Pellegrini said it was a good decision.

In the OED there are no examples of persons being offloaded from public transportation vehicles.

I would nonetheless adjudge offload an appropriate idiomatic use, though it does carry a very slight implication that it is being done against the passenger’s will. Where we speak of offloading passengers, and would this statement work differently in a civilian environment, would somebody disembark and move off?

In the OED, there are some examples of humans being offloaded, e.g. being injured or dying. 1967

M. Woodhouse Rock Baby v. W.E.C. 43 A Director who has to offload one of his staff and is embarrassed. Oneyear,

2001 Four FourTwo Sept., 2001, dated October 25, 2001. Lazio made demands on Italian forward Manuel Pellegrini for Juan Sebastian Veron but obviated his ‘worst’ bid. Pellegrini said it was a good decision.

In the OED there are no examples of persons being offloaded from public transportation vehicles.

I would nonetheless adjudge offload an appropriate idiomatic use, though it does carry a very slight implication that it is being done against the passenger’s will. Where we speak of offloading passengers, and would this statement work differently in a civilian environment, would somebody disembark and move off?