That is one sweet upgrade
That was done because the resort booked the Royal Rooms expecting them to be completed and they were not done in time.
That was one time when Disney did feel that they greatly needed to make this up to their guests. Not only was it considered a refurbishment of the resort, but there were very special themed rooms that had been especially pressed via marketing by Disney.
This is one time when they felt they were greatly inconveniencing their guests and thus the upgrade from moderate to deluxe.
I can tell you it was mostly a huge disappointment at first for many of the guests who we followed on the POR thread. It was great what Disney did and almost all of the guests were pleased with the choice of the Poly in the end.
But you can imagine their disappointment of just barely missing getting into the new rooms; some whom had booked months in advance.