I agree with this, for the vast majority of the girls. DD wore a short skirt at school, with thick black tights, because that was what all the other girls wore. Nothing to do with boys, or being provocative, she just didn't want to stand out from the others
Well, yes. I wanted to wear a miniskirt when I was seven years old. Because it was fashionable.
But that does not mean that the fashion was not influenced by the male gaze.
It is the cultural double standard that adult women have to please males to get somewhere (obligatory high heels and leg-shaving in some jobs, even), but when girls try to imitate those successful older women, trying to do it even better, as is only natural for children to do, then there's an outcry.
The obligatory sexual objectification of adult women, combined with morals that oppose the sexual objectification of girls under 18, naturally results in girls under 18 being denied the completely normal teen behaviour of imitating their idols. Which, of course, they will resent.
If you allow girls to dress how they want, you have a decent chance they will choose a different way to "coolness". (When I was seven, I also wanted to have green hair).
But if you force girls in a sexist, male-gaze oriented culture to wear school uniform with skirts, you really have it coming.