That's not how it works, OU is a % thing. Basically the chances of you seeing that Pokémon at least once in 20 battles, being strong but having huuuuuuge issues in being put on teams due to being a harder to support version of another mon, or outright having no niche or poor support options would end up dropping a big stats or nuke Pokémon to UU, or if he is too centralizing there to BL.
OU doesn't mean power, OU means being reliable, just like latios, pivot Lando T or Talonflame wich flagship isn't offensive brave bird, but actually the specially defensive set, look at good old Salamence being borderline by being a mediocre dragon with the only niche of mixed scarf moxie and wish shuffler being the only sets he is able to pull of when compared to other dragons.
I doubt GF follows Smogon either.