Is there any real evidence this is the case? I haven't seen any indication that places with stricter gender norms around clothing produce more gender dysphoria in kids.
Is there any reliable evidence for anything when it comes to gender dysphoria?
It would be great to see the evidence or for academics to be able to study it, as I agree that it's most frustrating that we're in a climate where we all just have to speculate,
My thinking on this is all anecdotal- from my own experience of raising girls and a boy, my own experience as a gay and neurodivergent 'weird' child, my experience of listening to trans people's and detransitioners' experiences of being confined by gender expectations and from the DSM-5 criteria for gender dysphoria, which relies on non-conformity with gender norms for the most part to make a diagnosis.
My sense from the transwomen I know and from hearing countless other parents of trans girls is that they were admonished for being "too girly" as children and usually at least one parent had a massive problem with that (Jazz Jennings' dad, Susie Green's husband, etc). My ex-DH was like that too, but we separated when DS was very young and then he was free to grow his hair (because he wanted to hide behind it, not because he associated it with being a girl) and wear the dressing-up clothes his sisters were wearing. I don't know what would have happened if I had listened to those around me (his dad, my mother, etc) and had told him he can't dress like that or play a game because he's a boy, but I can absolutely see why a little boy who desperately wants to dress a certain way or play with his sisters might become distressed about being a boy when he is constantly told it restricts him in ways that socially exclude him. And DS would have been incredibly distressed about not being able to have long hair as he desperately wanted/wants to hide his face (he has ASD and a minor disfigurement, which obviously isn't minor to him). And then when a little boy who's growing up thinking "if only I were born a girl" gets to school nowadays and is told that you can be born in the wrong body and you might be a girl on the inside, that would make perfect sense to him and be incredibly appealing as a concept. DS knows he's a boy but he is in thrall to the social media narrative that TWAW and if he were younger (he's in college now) I know he would have jumped on the idea that he's in the wrong body as he struggles greatly with his disabled body a lot of the time (and he still might identify as a different gender as he's in that culture and it's a hugely appealing concept).
I also think that there's a positive link between enforcing gender conformity in little boys and gender distress because places that tend to be very homophobic for religious reasons (which is the strict enforcement of a key gender norm, through shame, social exclusion, etc) such as some countries in the Middle East and large parts of the US appear to have a tendency to transition gay people to make them more socially acceptable within the confines of those very strict gender norms around people you can have relationships with (and whether it's ok for a man to act effeminate or not).
When you listen to transwomen who transitioned in middle age, a great many of them say their gender distress started in childhood when they were told they couldn't do x or wear y because they're a boy.
This is also a large part of the DSM-5 diagnosis for gender dysphoria - playing with toys or wearing clothes associated with the opposite gender are taken as indications of gender dysphoria so I don't think it's particularly 'out there' to believe that at least some gender distress in young boys is caused by rigid gender stereotypes being pushed on them, as the very definition of gender dysphoria, rightly or wrongly, relies on the strictness of gender norms and suggests that any deviation from these strict norms is a defect in the patient, and kind of makes the assumption that societal sexism is a good thing.