The only thing I've heard is that the costumes for L&S are "owned" by Disney-MGM Studios. Stitch is appearing in various cars in their parade, and after the movie opens will have his own car. The Polynesion is part of the Magic Kingdom. Magic Kindom and MGM are in "competition" for guest dollars, MGM wants exclusive rights to the costumes to help their numbers so is heavily restisting L&S at the Poly.
Same thing is going on at DL. L&S will be appearing in the Paradise Pier section of DCA, over by Pizza Oow Mow Mow (or whatever it's called) instead of Adventureland, because DCA has attendance problems. They're hoping a Stitch meet-n-greet will get a few more bodies through the gate, forget that PP is a California amusement park setting and L&S is supposed to be Hawaii. The pizza place is themed like a surf bar, which is "close enough."
Corporate politics at work again. Yeah!