Even if there's "pushing" of het romance the main focus are those two, the "het romance" can be pushed how much someone want, it's still shounen-ai and the two have a solid relationship/friendship since volume once.
Any kind of romance added later is already a lost game even if no one ends Canon because the Manga is still a shounen-ai even if they don't directly end up together (Like Shinsekai Yori where the end couple is a mixture of a genuine relationship and the fact that they were the only two left and decided to date because they lost their same sex partners, Banana Fish and No.6 where they didn't get together and Erased where the MC didn't end up with the girl he saved which I think is fair, the other love interest doesn't feel like a love interest plus he could be her father since she's 17 and he's 29 and they have a more father and daughter dynamic the whole time, the only proper love interest is the man who was responsible for the deaths who was the only one always with him after he ended up in the hospital who loved him more than anyone else did and there was definitely some reciprocal feeling from the MC as well in their own twisted way but he got arrested)
should be taken off shounen ai tag cuz of the pushing of het romance constantly(“healthy boy” headass),, but still really fun :))