I don’t think the AU is shared
Yeah, it seems somewhat unlikely.
I'm still kinda mind blown at a universe where SasaMyaa aren't wide open, and all because Hirano wasn't dating a guy at the time when Sasaki confessed. That's a much more basic scenario for BL.
Like, normal SasaMyaa just had a conversation about boundaries with that, but "if it comes up, I don't think it's a big deal to say," but here we get "Oh, nothing, haha."