It would not be fair, because the point of having divisions is allow women to compete in a competition that is not dominated by men.
I think you're falling for Sticker Swap Fallacy. The goal is to have fair match-ups in sports. Gender and sex are two possible labels to use to assist with this, but they're imperfect enough that we probably ought to not use them as the primary differentiator.
https://www.lesswrong.com/posts/C7LcpRtrHiKJRoAEp/sticker-sh...
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> It would not be fair, because the point of having divisions is allow women to compete in a competition that is not dominated by men.
Really, what it is is being dominated by Testosterone. Also why we ban steroid use, and many other things along the same lines.
I would suggest that most Olympians - both female and male (whatever your definition) likely have a higher than normal amount of that hormone.