There is no reason to not make it available for all players. Literally none. You even lose it after premium stops.... Most games at least let you keep premium stuf like this after it stops or dont make it part of the premium at all.
There is also no reason that they cant do this, they have changed enough in the code, so there is no reason they cant change this.. hell its easy to change it but i wont go into that,.,,
Its the only reason why i dont buy dragon pouches and costumes.