that's one of those things that is kinda questionable. on one hand, the item was never given out. on the other, the poke was rng-ed normally. i know pokemonGTS and pokecommunity consider it hacked even though it was obtained normally after editing in the item. i'm fairly certain i've seen them on here before, though, and no one has cared. it's one of those sort of personal judgement call things. for me, i know it was obtained in a legitimate manner after adding in the item and i think that adding in the item is forgivable since nintendo never bothered to distribute it. not everyone will see it that way, though, i suppose. i know i've definitely seen shiny perfect arceus here before without a problem.
i assume you're talking about this guy right below me?