Both of you have hit the nail on the head when it comes to how it feels as a maturing girl.
If you grew up in the late 90s to early 2010s, then you will remember so much media that associated femininity with being a giant, huge slut or mean, vain popular girl. Cheer captain? Slut. Caked in makeup? How desperate!
Now add the layer of being a young girl suddenly sat down and lectured about abusive dynamics, date rape drugs, and being aware of your soundings at all times - it completely sours your ideas about romance almost immediately.
When you hit the age where you are suddenly having those feelings, for boys, nobody cares or is surprised because you're a girl turning into a heterosexual woman.
But to you, your sexual awakening is the most important thing in the world, completely unprecedented, a little scary and forbidden-feeling. Where in media (etc.) do you see that feeling portrayed, with as much importance as it deserves?
It made it so hard as a young girl to enjoy painting your nails and wearing makeup because it made you feel like you were trying to be that slutty, mean popular girl you saw in every show and movie. Not to mention feeling like the fattest pig in show if clothes didn't stick to you like they did cartoon characters. The nerdy book girl or the goofy, fat girl might be the protagonist but she was always ugly, weird, or awkward.
These girls feel too ugly to be girly or feel that being girly is directly offering yourself up to be objectified. They really think that if they say they're boy, then they can enjoy makeup and feminine clothes without being judged as women are. Being a soft, gay boi is vulnerable, nuanced, enlightened state of being while being a basic, straight girl is some factory standard that needs to be escaped.
If a girl is like 12, or has those comorbidities, the option to identify as a boy must sound like "choosing" to approach boys as an equal in the power dynamic (you're the same as them! you don't have girl vulnerabilities or do things for wacky denigrated girl reasons!).
The media didnt help them then (
those Olsen twins are FAT PIGS - 2002) and it doesn't help now (
Like pants? Hate bras? You might be FtM!). Even with all the promotions about how "women can also fix tire! women can even be astronaut!!", it has always been girl-power-lipstick bullshit that most chicks dngaf about. Instead, it convinces normal, non stereotypical girls to throw themselves into a standardized pooner box sinces it's predictable and safe..
"I don't like how makeup feels and low cut tops fit me, I feel uncomfortable with guys commenting on my figure, I'm afraid to wear such a cutesy dress since I'm worried about what my highschool friends might think .... Guess I must be a boy! All girls love those other things!"
Tldr: Pooning out becomes appealing when you already feel like the ugly girl. Not much different from a failson who goes AGP, they think they can change teams and enjoy different outcomes. It's why they all meld together after awhile, they have a single "trans" identity, not their own. They hate themselves so much that they'd rather turn to jelly and fill a mold than just be whatever they already are.