Canada

I think the main question is consent, who is consenting and the legality of it along with liability.

The question is a legal question and what is consent along with what is the responsiblity or liability of the doctor.

Typical medicines are not natural, but are legal because the consenting party is the adult on behalf of the child and recommended by the doctor.

For medicine, diagnosis and treatment are done determined by external actors.

Feel unwell -> cause determined from outside perspective -> solution prescribed from external perspective -> feed back from patient.

I think for HRT, it's more murky legally. For transition it's more self reported.

Feel unwell -> self diagnosis -> self prescription -> reporting to oneself

Gender dysphoria is being removed as a diagnosis so external diagnosis by a doc and prescription based on said diagnosis cannot be done.

And the child in question consents, not the parent.

The way medicine has legally operated is not reflected in transition.

If transition was possible without medical aid, it would be different. But it is not possible for humans to physically transition, unlike other species who can.