I can see how this proposed idea is logical in terms of taxonomy, like it works in a vacuum, but the problem is it's not really fixing any of the problems we have here.
Romance (all forms, including GL, BL and some in LGBTQ+) is the biggest genre on Tapas. The entire reason it was separated out like it is was because it's so massive and that the BL was overshadowing the het in popularity so much that when they're in a single category, you'd go to "Romance" and get a list that's almost all male/male. By making the user need to then narrow their search to "straight romance", you're adding another click to the equation.
Assuming the comics are listed by popularity, in this proposed system, the user clicks "Romance" sees a sea of BL and one of three things happens:
1. "Oh huh, all the biggest titles are BL huh, I guess I'll read a BL"
2. "But I want man/woman...err... ah here's a button, let's add the het filter..."
3. "WTF does this site only have male/male!? I'm going to Webtoons!"
In all the cases, this system would result in a comparative loss of sub gain by the people making heterosexual, LGBTQ+ or GL romance. Because they need an extra click. Extra clicks matter. Hell, extra scrolling matters! I've been featured on the front page three times. Once in Staff Pick, right near the top of the page, resulting in increase of over 200 subs, once in Community Pick, which is in the middle of the page, resulting in about 60, and once in a collection that was at the very bottom of the page, from which I got about 20. It's basic UX that the further a person has to go and the more clicks are required to get a thing, the less that thing will be found or used.
You have to build the taxonomy around what the user is looking for and what the creators are making. A lot of people come to Tapas looking for queer content because wow, if you're queer and you're browsing Netflix for stuff, the options are slim pickings, so we're pretty hungry for new content and our primary interest, above the genre, is "does it represent my queer experience". This proposed system fragments the LGBTQ+ content on the site into Action-LGBTQ+, Adventure-LGBTQ+, Romance-LGBTQ+ etc. Making it less visible, harder to find and less financially viable for the people making it. Making the site conform to how bookshops organise works and a nice, neat structure based objectively on "what is the genre though?" may feel satisfyingly neat, but it wouldn't help users find what they want or creators feel findable in their categories.