[a_shovel]

Puberty blockers for transgender and potentially transgender teens aren't meant to be taken all the way through to adulthood, if that's what you mean by "otherwise stopped growing." Ideally they're taken just long enough for them to get counseling and come to a decision, a couple years at max.

Apart from that, "different use case, different intended goal" is cause for what I'd call "ordinary levels of scientific uncertainty." A 13-year-old just starting puberty is not so different from an 8-year-old just starting puberty to justify denying a medication to one by law while still prescribing it to the other without concern.