Sometimes people push bills like this to make their opponents look like fools, though maybe that's not as common in the EU. Movements are infiltrated all the time. I don't know the details of that bill (much less the name or backers), so I can't really comment.

What I do know is there's tons more bills trying (sometimes successfully) to block consenting adults and older kids with parental permission from even basic stuff like counseling or blockers. That seems way more dangerous than the fraction of a percent of kids who change their mind later being able to go through with a transition they'll regret.