Nintendo's methods of stopping hacked pokemon are far from perfect I've heard, perhaps this is evidence of that...
A friend hacked a level 70 shiny Azurill caught in Pinwheel Forest or something like that and gave it to me, Pokebank said it was fine and let it through.
Then I have an legit Arceus with Pokerus, and the bank says NOPE, NO HAXING!!!
Nintendo's methods of stopping hacked pokemon are far from perfect I've heard, perhaps this is evidence of that...