Forget it, folks—this is the implacable Grand Inquisitor of Yuri Manga:
“Truly I say unto you that it is easier for a camel to fit through the eye of a needle than it is for a story to earn the title of ‘yuri.’ And if it even contains a male character?—fuggedaboutit.”
Only the Inquisition (or more properly Inquisitions; one was set up to cover a specified region as needed and was quite separate from others of its kind elsewhere) actually had, and mostly stuck to, pretty stringent rules about proof and evidence. Which is incidentally why they tended to take a very dim view of witch-hunts as mere superstitious hysteria.
Meh I don't care, judge me what you want, I have my favorites works here, anyway this story I did only read it 7 chapters and I got bored after that...so with this happened I'm choosing very carefully what I read, etc.
My rule: Yuri must be Yuri, het must be het, Yaoi must be Yaoi, any of those can't get mixed because they're very different...
That count even the brother is trolling his sister
Besides, with more of 30 chapters and no noticeable advance, I suggest a reconsider of tag
Yuri Crush
Subtext
Your bizarre genre-apartheid dogmatism aside you're literally and glaringly contradicting yourself here. If you dropped this - deliberately slow-burn, one might add - series after mere 7 chapters (emphasis added to quote above) then what can you possibly even KNOW about where the narrative stands at over five times that number, and why exactly do you think you're still at all qualified to pass judgement on what tags it should/n't have?
Or for that matter, that you're at all relevant to the discussion in the first place?