So....do all Pokemon used in Rated Battle Spot battles have to be blue pentagon or something?
In official tournaments in Generation VI, as well as at the Battle Spot in Pokémon Omega Ruby and Alpha Sapphire, only Pokémon with a blue pentagon can be used.
The above was taken from bulbapedia so yes is the answer. Id guess its to limit the hacked pokemon from pokeedit and the likes which were prevalent in Gen4/5. Of course it doesnt mean much after the PKHex stuff was released.