To me this runs into at least two challenges (that I've already outlined). Foremost, how much is enough? TTRPG isn't played to the standard of scientific investigation, nor of expert consultation or testimony. Not all subjects matter equally. Lack of expertise in quantum mechanics is unlikely to make a difference to the experience of living in the Inmost Sea. Strong knowledge of the Earthsea texts will matter more. Secondly is that when the imaginary world is one created by people at the table, those people are its foremost experts.
I'm thinking of the original FKR practice as well as the so-called Revolution. I don't think FKR adherents will mind that you think they must be above-average GMs

I would agree with a sense that successful FKR simulative play is more achievable where GM's knowledge of subject is stronger than players'. That allows players to immerse and not worry about upholding the "pretended realism" of the imagined world.