There seems to be some debate on this. Apparently, there has always been a sign saying that the FIRST ENTRY is reserved for DLR quests. It was not enforced very often but now appears to be. So for all other guests, their first entrance of the day must be through either CA Adventure Or Disneyland Main Gates. After that, you can still hop from CA Adventure into and out of Grand Californian Hotel. This probably is tied in with the closing of the PPH entrance into CA. Since PPH guests now are encouraged to walk to the GC and use that "exclusive" entrance, they probably needed to make it more enclusive to seem like a perk.