In sports, the main reason why men and women compete separately is that men, due to differences in hormonal mix and development, quite simply grow stronger muscles, and on average also grow taller, than women. It's a matter of biological, physiological sporting fairness.
So I can see, and actually support, that transgender folks who are treated as women socially are still treated as men athletically, if they (still) have the male mix of testosterone, size, muscles etc.
Or else, next thing we have a boxer claiming to be a feather weight trapped in a heavy weight body!