You do know the chances of getting a Pokémon with all 31 IVs AND good nature AND shiny are extremely slim, right? I'll eat my hat if Pokégen is banned next gen yet we still see a Pokémon like this. The odds are completely against the player.
And RNG is cheating as well. You need an external program (RNG Reporter) to even find your seed and calibrate your DS. How's that different from using an AR? It's even an improper way of cheating, since, if you know what you're doing, you can replicate a Pokémon with Pokégen and Nintendo won't even know it was hacked.