I thinks it's unfair to have a DLC be timed in general, however it is economic, Sony paid them crap load of money to make sure Microsoft gets the short end while Sony gets the PR and exclusives. However another part on Bungie is also a factor. They could have made an agreement with Sony and sold themself to them and become a first party publisher and keep Destiny as a PS exclusive. Yet they decided it was better to sign on to Activision and make the game for both sides of the party.