Actually, that annoys me as well when the author (and it's usually a non-slash author) has to insist that these character were DEFINITELY NOT EVER EVER LOVERS rather than just write a perfectly good friendship story without having to set boundaries, especially as it's usually same-sex characters getting this treatment. I think the only het pairing where I see much of this is Joan/Sherlock from Elementary. Personally, I don't want to see them as lovers, but it's quite a trip to see people write fic where a man and a woman are DEFINITELY NOT EVER EVER LOVERS when usually it's a potential slash pairing. Even Mulder and Scully noromo fics didn't get that level of vehemence!

Then again, this was vastly worse in the 90s in the days of smarm, I think: extremely intense emotional manly friendships with a big NOT GAY sign over scenes of them naked cuddling for warmth.