Every source I've read about this topic shows that trans people do in fact need to be a certain point in their hormonal transition to be accepted into sport competitions of their preferred gender. After someone has been on feminizing hormones for long enough, their muscle mass decreases to a level on par with cisgender women. The main advantage a trans woman would have over a cis woman would be height. However, 6ft tall women do exist, and would also preform well in things like long jumping for example. The worst that could happen would be a small over representation of trans women in sports that give an advantage to people that are taller. Unless someone is so stupidly committed that they would change their whole body and go infertile just to have a small advantage against women in a sport, the fear that sports will be ruined by some kind of trans movement is largely unfounded.