"not all trans girls ... want to wear frilly pink dresses or play with dolls. We ... see plenty of trans kids violating these stereotypes, just as we see cis kids do"

Bingo. I never showed any interest in "girly" toys as a kid and I'm still trans. https://www.newsweek.com/transgender-kids-living-identity-develop-cis-children-1471729

Gender stereotypes actively hurt me. I didn't "always know" I was trans. I grew up in a very gendered environment. As a kid I was mostly interested in playing with legos, tools, and plastic swords. Because those were "boys toys" no one ever bothered me about it.

Dysphoria didn't really hit until puberty. All the sudden I was aware of all the expectations of what a "boy" was supposed to be. I knew I didn't "fit in" with those expectations, but at the same time I didn't see any other way I could be. I ended up cutting myself off.

For a long time I didn't feel like I was even a person. Because I had some "masculine" interests I thought that was what I had to be. It's what I was raised to be. As uncomfortable as it made me, I forced myself into a mold because I was afraid to break some unspoken gender rules

I didn't have many positive examples of femininity to look at either. I am very much a gay woman. Lesbians don't get much representation in media, and it certainly wasn't coming up in Sunday school. As far as I was told, women were supposed to be delicate, chaste, and subservient

I wasn't exposed to the LGBT community till I came to college. Even then it took me three years of slowly experimenting to begin to undo those biases. It was less that a year ago that I finally became comfortable enough with myself to accept that I am a trans woman.

If I hadn't felt so constrained, either in my conception of "masculinity" or "femininity" I would have started experimenting years ago. I wouldn't feel like I'd been robbed of an adolescence. So please, support your kids regardless of their gender expression.