Perhaps freelancer didn't put particular area of their expertise in their profile, which I believe they will be missing opportunity not to be caught by search features.
It seems so, yes.
At this moment I have found 17 pages of freelancers claiming to have R and Python skills so somebody could know how to do what you want probably; Is just a question of keep trying. Not me , I'm not expert in PSO or multiobjective and my Python is basic (I can call myself an R expert or "sort of" without blushing at least) but If you can suggest other common term grouping those techniques, the name of a software of choice, a desired country or language or a desired rate interval I'll try to refine the query for you.
To be honest, the fact is that I should thank you for asking this question. Is an interesting problem and I'm learning a lot about how to move faster and better in Upwork while trying to solve it. (More 'superpowers' to me, yeah, never enough ).
So if you want to provide more context, there is still a reasonable pool of eligible candidates.