Its a very tough call, because there is a window where you want to slow or halt puberty by your current hormones to transition, and unfortunately its the same time as developing the brain.

There are legit people who are just born and know there brain doesn't match their assigned gender.

You will have those that may have a disphoria disorder, where the brain tricks them, like people who have alien hand syndrome. And so do you try to treat that via mental health, or do you give them relief by having a path to changing.

There will be just some kids who don't know their belonging in the world, and feel the gender change is the answer. (We were all confused teens at some point.) These kids I feel really bad for because they may think the transition is going to solve how they feel inside, but it might not, or they might grow out of those feelings.

But back to the problem, if you ask them to wait and see if they grow out of it, you've lost valuable hormone time, and had them suffer unnecessarily if their outlook didn't change.