Most people, and politicians seem to accept the current rulings that people can't have sex until they're 16, and can't go out drinking until they're 18, with the reasoning being, as far as I can tell, because they might get pressured into it, or even if they want to at the time, they might regret it later. I'd say the consequences for making a poor decision and regretting it later are much greater here.

That said, and while I do think that pushing gender/sex conflation religious psuedoscience on confused kids is messed up, in this case, the hormone blockers alone are unlikely responsible for the noticeable changes to this lady's face, like facial hair, which I guess come from taking male hormones at a later date, possibly as an adult.