It's ALWAYS been a sub-genre of romance. No one has made enough of a convincing argument, based on narrative merit, to even raise it to a hearty debate. It's always been economic reasons.
My argument here has always been about the logistics of genre categories with a sub point that Identity/representation is a point of sub-genre. If you want to argue this is my "misunderstanding" of a need for identity/representation, then you'd be better served choosing a battleground other than BL. I defer to other folks, closer to the topic, analysis that it's often being wrote and consumed by others that "non-default". Is that a bad thing? I don't think so, but I believe it means it's potential staying power for dominating the medium has a shelf life.
I guess it could be easy to assume that was ALWAYS their plan. But when they introduced BL as one of their categories, it came with lots of explanations about how unworkable it was to add more categories or give the "rabble" (my term, not their's) access to a second genre listing. Now with the addition of two more representational categories and the rumors of a second genre for the "rabble" and a third for the Upper crust, it seems the technical reasons for not doing this sooner weren't as unworkable as we were told.
Make of it what you will.