I’ve used Baz’s requester for several years, but if you don’t feel comfortable using that, maybe you can use solicitor, petitioner or

supplicant. I do in particular prefer those who use Baz’s requester but can’t quite use it yet.

I think that the term you are looking for is multiple discovery or perhaps convergent invention.

As Janus says, if the context makes clear what you are talking about, you could just say this. If you want to use synonyms, maybe you could use tendency, trend, behavior or demeanour?