If true, this is recent. Not long ago, girls wanted their periods and were bragging about getting them. The popular girls were developed and menstruating and the rest were considered little girls and unworthy. It’s amazing what can change in a mere generation - if it’s actually true 99% of girls want to avoid this.
There was a whole event around puberty: first training bra then real bra, from Cotten panties to silky, to pads then tampons. Every girl read Our Bodies, Ourselves. Girls couldn’t wait to be women.
I think it's a little of both.
Your mom hypes up "becoming a woman," school has a filmstrip and everything, your peer group brags about their bras and who's started menstruating, and it sounds great and desirable at the time. But you get that early-boob-grower one on one and talk about it, or when you get your own period after months of speculation and wishing, there are doubts.
I think trepidation about female puberty is normal. It's a change to be adjusted to, and any change is difficult. Wishing to be a "kid" again, not a potentially-sexual being, is universal if more fleeing in some girls than others.
The problem is, like you said, the culture around it is different. An individual girl feels the same ambivalence as she would have in, say, the 1970s, but the peers and "affirming" adults are celebrating gender transition in the same way they used to celebrate becoming a woman.
Being a woman used to feel transgressive, when feminism was about equality. Now being a woman is boring and Establishment (unless you're coming it at it from being male) so if you want that same feeling of daring and being up-to-date, you have to be NB or FtM. Your
mom was a woman, and she's so lame.
My own poor analogy: you know how girls like to read and write fanfic about gay dudes realizing they're gay and fighting internalized homophobia, and that can turn into aspiring to be a gay FtM? I think it's from a girl having a sexual awakening, and wanting the world to recognize how weird and revolutionary that feels. But she's just a boring heterosexual like most people; your own puberty is only interesting
to you.
The closest
emotional equivalent is a story about a dude figuring out he's gay. It's transgressive and a little forbidden, the same way being newly attracted to boys
feels to you, except other people actually care about it and don't just joke about being a boy-crazy teen. Maybe this means... maybe
you're gay, but in a way that lets you like dudes?
Anyway, the future is terrible.
edit: typo clarity