The difference is that a blanket ban, even a temporary one "just in case", is actively hurting children. In the UK, trans teenagers need several years of counseling and doctor visits and jumping through hoops before they can actively start transitioning. These drugs help at least halting puberty, otherwise total transition is much harder or impossible. I don't think these drugs should be easily accessible, but right now it's already so hard to get, that kids are getting them from the dark web in secret!
Sure, there are bad parents, and abusive parents. But you can't justify saving children by hurting other children. I'm not "assuming" anything. Defending this ban is literally hurting children.