A big issue I’m seeing is that people are here for the romance but the romance was never the mangaka’s focus, lol. And the writers of the drama decided to stick to the story rather than make any significant changes.

But from the authors notes on the manga volumes we know that the first volume was meant to stand alone, it got serialized in a BL magazine so the story had to include some BL. 

Then it did well enough that they wanted a sequel, so to jump start a new story she brings in Maya. Her editor is like “this is a BL can’t they get together?” 

In another authors note at the end of Limit she talks about new side characters and wanting to flesh them out and how happy her editor was that the boys were finally dating. She says at one point “come to think of it have I even shown them acting as lovers?” Telling a love story was not this author’s top priority, lol. She wanted to tell a slice of life coming of age story around disability that just so happened to get serialized in a BL magazine by the sounds of it. And did well enough that people kept asking for more of it

This is just my speculation based on the author's notes. It really does sound like writing a BL was kind of an afterthought. Personally I love slice of lif stories so this really works for me.