Legitimate, genuine, non-trolling question:
Why would a non-binary athlete compete in the category corresponding to the sex the athlete was “assigned at birth”? (I am deliberately not mentioning any current examples by name, so as to reduce risk of inflaming anyone).
Likewise, say you’re non-binary and want to run Boston. What qualifying time do you have to run? There’ve been athletes assigned male at birth, as it were, who now identify as female and thus have been given Boston entry using the women’s time (I went to college with one such athlete). But what about non-binary?
I think logically, the allowance of a non-binary athlete just continuing to run in the category of assigned at birth/biological sex actually reinforces the argument that such competition categories are best defined using biological sex.