"To preserve fairness in and integrity of the women’s category as well as equity for trans, the necessary and sufficient condition is to institute eligibility policies that ensure that the fraction of trans women winning medals as a fraction of all trans women is comparable to the fraction of cis women winning medals as a fraction of all cis women. Finding such policies needs continued research and (unfortunately) some real-world experimentation, but WA and FINA have ensured that the fraction is practically 0 for trans women today."(quote)
That is a false argument. "Fairness" isn't shown by how well trans women do against other trans women but against women. It also isn't necessary to conduct studies of how well trans women perform in sports to know they have a biological advantage. Take away their "identifying" as female and we are left with the fact they are males competing against females. That isn't accepted because it is unarguably an unfair advantage. It isn't changed because some individual trans athletes may be much better (or, conversely, weaker) than others. We don't let inferior male athletes compete against better women, either.