eh no they totally can, the author just wasn't interested in that or didn't thought the story in that direction
there's lots of manga about trans characters, and yes those are harder to publish commercially, but its not impossible
also, BL *is* mainstream, its not some underground genre and there're whole publication houses dedicated to publishing just BL
anyways, just by reading the end note we can understand that the author doesn't think of Sakura as an actual (trans) woman, they just made an overly feminine guy that ended up as a convincing representation of a trans person
ah tbh im not sure my point came across properly
im not denying your explanation, its very real that oftentimes stories don't develop much because of strict chapter lengths (it happens in pretty much every genre unless you get lucky), but for this specific manga its because the author didn't envision their characters like that
i said that because there are trans romance stories out there that have 5 to 7 chapters, so its not impossible to develop or include that part of the character's identity
A lot of the times when a manga ends i go to the comments and people ask why A plot point wasn't developed further, in this case whether mc is a trans woman or not because of how he feels. You all, let's not forget bl manga are still a lot of the times publications, sometimes even monthly and they are given budget or the go sign for 5 chapters + extras. It's rare for bls to get more because they are not mainstream!!!! There is no time to develop further plot points other than the 2 leads falling in love because they have 5 chapters + extra and they cannot "waste it" into topics that won't create love or develop the relationship between ml and mc