It's not very clear what you're saying, but if it's that a researcher must assume that they have free will in order to test for whether there is free will, I think that's pretty much uncontroversially true. However, I don't think that it's problematic, it's only problematic if the researcher attempts to test for complete absence of free will. In this case, the researcher would be unable to consistently draw the desired conclusion, due to the conflicting assumption.
Thanks, and thanks for the reply. I've noticed that it's the popular choice on internet science fora, of my experience, but I'm somewhat surprised that the physicists themselves are realists about any interpretation.