I'm certain he'll find some way to mentally contort himself and make that utter non-change to current policy a good thing. Like exactly how many cases have happened where a doctor trooned out an actual child without the parents' permission? I guess if we include teens it might be somewhat noticeable, but it PALES in comparison to cases where the parents are full-on bought in and/or literally imposing it on their children as some kind of fucked up Munchausen by Proxy type of deal, none of which would be affected by that. Of course though, it's mostly women doing this shit to their kids statistically speaking so acknowledging that would harm Jershy's little feminist worldview.
If Trump had any balls he'd just flat-out ban puberty blockers from being prescribed for gender dysphoria and ban cross-sex hormone treatment for under 18s at a bare minimum. There's no sane argument for kids/developing teens being allowed to undergo those kinds of treatments even WITH parental approval, it's just plain bad for you even as an adult and it's worse when you're not one yet. But of course, he doesn't have any balls, so he won't.