Yeah given how readily they administer all the other irreversible medical interventions to young children I'm pretty convinced the reason they aren't doing as much bottom surgery isn't any kind of concern about informed consent. The most likely reason it's less prevalent is the same reason they don't do certain types of orthodontic surgery until you're over 18-20; it's just a waste of time to do it whilst you're still growing, it'll grow out weird and they'll just have to do a second corrective surgery later.