This is nothing new. 30 minutes early for resort guests is just like EMH, only it was one hour.
All guests were let into the park. At MK, they had CMs at each spoke of the hub, if you wanted to pass, they asked you what resort you were staying at, scanned your MB to confirm. If it showed you were a resort guest, they let you through to go on rides. If it did not, you were asked to wait until official park opening.
The 30 minutes early, will likely be slightly variable, just like park entry is, and has been. There is no guarantee that the park will open early-or even on time, but it was not uncommon for it to open even just 10 minutes ahead of posted,. Currently, they are opening far earlier than posted, as others have said, to spread the entry crowd thinner.