Lady Business

I relate to this so much, ahaha. I remember as a teenager going onto scanlation sites, some of which had a specific filter/tag FOR crossdressing alone... Found a lot of gems that way. But like you said, there was a shocking undercurrent of heterosexuality among almost all of them. I remember being upset a lot of the time when a girl would fall in love with the cross-dressing girl but then have to give up on that love bc the cross-dressing girl inevitably had a male love interest... Come on!

However, there is something special about that somewhat ambiguous state of both heterosexuality AND queerness that those stories evoked... Though the main relationship(s) are typically M/F, there's an appeal in a M/F relationship that can start with the basis of male friendship--sharing a friend group, all-boy's school, club, work, whatever allows for a platonic ideal of courting that prioritizes foundational friendship rather than JUST "we're a boy and girl so we gotta get together". Although it's somewhat common for the male love interest to know she's secretly a woman, she nevertheless is allowed into the male spaces, and she gets to be close to her love interest in a way that she wouldn't be allowed to as a woman. And if the male love interest DOESN'T know her gender and interprets himself as gay, then there's also an appeal to the vibe of "He loves her so much that he is willing to go against all of societal conventions" (though there's a certain gender essentialist tint to that "he can only fall in love with a man who's "actually" a woman" that's uncomfortable when examined). Overall, a girl-dressed-as-boy gets an opportunity to be freed of her usual gender expectations, which has a huge appeal for both queer readers and women in general who wish they could be "freed" from sexism.

That ambiguity feels like the precursor to queerness, but tends to default to the "proper" cisheterosexual state by the end. A lot of endings involve the girl "growing out" of her cross-dressing tendencies (Ouran High School Host club manga felt like a particular betrayal when I read it... what do you mean this gal who's expressed so many agender thoughts has now decided to present entirely feminine with long hair and a skirt?), often still positing marriage as the ultimate end goal/state for the woman. Which perhaps is part of how certain creators "got away" with presenting a queer work to publishers: Yes, this woman cross-dresses and challenges gender, but her love interest is still a man, and in the end she will become a "proper" woman, so it's okay for her to do all this gender-challenging stuff during the course of the story!

As heterosexual as these stories can end up, I think there was a reason I gravitated towards them when I was a teenager who hadn't yet confronted her own bisexuality. They present a form of M/F love that doesn't have to fit in the exact M/F gendered box, plus a "safe" kind of F/F love/crushing (where girls can swoon over girls-dressed-as-boys), and so appeal to latent queerness while being "safely" heterosexual. There are stories which I might find disappointing nowadays (as my desire for explicit queerness has risen), but which resonated deeply with me as a child.

Nowdays I don't see so many of these stories, though it may be that I'm not looking for it. Your point about its absence from recent SFF makes me wonder, too... I've seen a lot of queer/feminist creators invent gender-equal/neutral (and sexuality-equal/neutral) societies for their stories. Though I have found that appealing in many ways, a sense of rebellion/challenge is lost. Many of the cross-dressing stories may feature cishetero women, but they are explicitly going AGAINST society in their journey, which is still relatable to a queer struggle. Meanwhile stories ostensibly about queer characters can sometimes lose that sense of marginalization/struggle when the society depicts the queerness as fully normalized. Not saying either approach is better/worse (I have loved stories where queerness is fully normalized and the characters are queer without that being the "focus" or struggle--other things can fill the plot/tension), but sometimes a "straight" story about a character hiding their true gender or true sexuality, with lots of plot points bringing gendered expectations and anxieties into focus, can capture a compelling queer struggle.

For some actual media I personally recommend: Revolutionary Girl Utena (the anime, not the manga) is a fascinating case, MANY things going on beyond the main girl "dressing in a boys uniform" (it's not the boys uniform really, it's something entirely its own but she's clearly a gender non-conforming character), but the story has a lot of themes about gender, narrative, and some explicitly queer characters. Plus, sword-fighting! Very 90's shoujo style but also a deconstuction OF 90's shoujo--check trigger warnings if you're sensitive to some common big TWs.

While I'm here, I just want to shout-out a silly crossdressing manga: Classi9, which involves a bunch of classical composers as pretty boys going to a music school together, with the central character being the Japanese composer Taki Rentarō--a man, historically, but in this manga he's a girl who has cross-dressed to attend this all-boys music school! Although I think it was canceled (it ends abruptly) it's a delightful little gem for people who like or are curious about classical composers.