If you try to define athletic divisions by sex, you're going to have a hard time. The world's best athletes probably all have some unusual biology. About 1.7% of people are not completely biological male or female. I would expect that proportion to be higher for Olympic athletes. Excluding 1.7% or 2% or 10% of the world's best athletes from competing would not be fair.

Anybody can compete in the unsexed category. It’s only the female sex category where someone can be barred. No one is barred from competing at the highest level.