I have one core set (yahoo for me) now why are the starter decks 48 48 48 cards and one (the Stark/Greyjoy) 47? Im thinking its because GJ can come back from the dead?

Well, really it's because the Fealty agenda takes up one of the neutral slots so there aren't enough cards to make the decks come out equal. The fact that the short went into the Stark/Greyjoy deck may indeed be because of the additional recursion, but your guess as for why is as good as anyone else's.