There's also the question of trans boys - if, say, a 14yo girl was transitioning to a boy, would they be allowed to change with, and compete against a cohort of 14yo boys? 
If not, why not? After all, the realities of the body are irrelevant to gender identity (obsessed with genitals? Transphobe!) and the other 14yo boys would in no way whatsoever stare/comment/be a threat to a female-bodied boys, oh no.
But if the trans boy continued to change and compete with girls, for (obvious) reasons of safety and fairness, that of course exposes the whole frigging charade.
Funny though, haven't seen this mentioned anywhere. All about the rights of the male-bodied girls.