huh. i never noticed that either. Wonder if the authir recived editor pushback or something and that's why girl had to be like "no i'm cis actually" once a book. Cause whatever they are it is not likely to be cis lol.
That could very well be the case.
For example, it's pretty common for Manga to have a "Crossdressing Episode", but even if the character ends actually liking it, once the Episode ends, they'll never do it again, maybe denying later on about liking it.
it seems to be fine to have for a short moment for funny antics, but not to do regularly.
If we look at Japanese culture, then there are many reasons why this could be the case.
Crossdressing, while more accepted nowadays, is still not seen as good by society at large, and that's even more the case for anything non-cisgender. So while they'll have a fun little laugh at those Episodes, they won't take it nicely to making it a normal thing.
So, most magazines and stuff will probably stop authors from going TOO deep into that, to avoid possible backlash. They'll allow it as a joke, a "Well, the character is forced by circumstances to do it, but wants to get out of it, so it's funny rather than bad" kind of thing.
I have seen cases of series that pretty much advertised themselves with the gender non-comformity of the protagonist, to then come out and discard the whole concept after Episode 1. (Coff Coff Vanguard Overdress Coff Coff) This most likely being the people on the top deciding they can't have that at the forefront of their products.
And considering that I have seen people actually complain and hate when an MC makes Crossdressing a common thing... I can't imagine how bad it could be in Japan.
Like, there was this Manga which name I don't remember with an MC that wanted to awake his Magic, but was a complete and almost invinclbe physical fighter with an incapability from birth to use Magic. So, after getting turned back into a little kid because reasons, he got recommended to try new things, open his horizons and see new things and perspectives of the world to attempt to open his magic channels or something like that. So, among things he picked up on Crossdressing, wearing a dress for a while. He wasn't opposed to it, and all his friends were very supportive of it.
But many of the Comments on the Chapters were pretty harsh about it. The longer it lasted the more they would complain and want it to stop already.
Unfortunately, the world still isn't open for Gender Non-Conforming Protagonists. Trying to get out anything like that in mainstream releases will inevitably come across a lot of pushback and complaints from the public.