Given the nature of this story though, I think the only concrete evidence we really need to confirm that it isn't BL, is that the author said so herself. Let me rephrase my original sentence: This feels like a BL, so I think it should have that tag. I'm thinking in the context for this specific site as well, and not based on the original. But this is a matter of my opinion.
And to put things into perspective, there is alot of BL content (even if it's all AU) for a non-BL story. It's still okay to do that, but the way it's presented here is not very...tactful, considering that the intended audience may not read BL. For an audience that's used to reading BL, this is probably next to nothing, but for an audience that may never have read any, I think it's abit too much.
Btw, I'm not sure if what you said are considered as spoilers for others, but putting the tag might be safer.