Sure this story is nominally against compulsory heterosexuality but the endorsed compulsory conventional femininity is a highly linked problem that's inseparable from comp het. "Even if you don't like men you need to be attractive in a way and act in a way that marks you as a legitimate target of men's affections" is how this compulsory femininity reads in the story. See the remark about Yuuko looking down on women by not taking care her of appearance in the "right" way. And yes conventional femininity is embedded in cis-heteropatriarchal structures in part just because those are the structures we live with right now.
There are reasons there are many, many, many works about tomboys who want to be feminine like their love interest. There are reasons there are very few works about butch x butch couples scanlated on Dynasty. Not all of the reasons why are evil or bad but it sure isn't neutral or random.
Compare Gender Game and something like Your Cuteness to this work. Both are against compulsory roles. Both are way less invested in compulsory femininity than this work is.
An aside: "Yuuko actually wanted to look feminine herself" is a terrible argument in this context. Yes this character has actual desires that aren't a reflection of the society and time in which the author wrote the work. Yep, it's feasible that all the fictional gay tomboys thought to themselves and all decided that femininity was for them despite how any IRL lesbian meetup looks. There are no authors and characters are all intelligent. Sure.