I would be really upset/disappointed if I had planned a trip around the expected MK hours for deluxe guests. While Disney CAN make the change with short notice, it’s poor customer relations.
I remember several years back we had saved up for a trip during Star Wars weekends for our daughter, and that was the year they announced they were canceling them a few months before they would have happened, of course after we had spent considerable $$ to book everything, and before Covid so plane tickets were basically non refundable. It was the start of the end of my love affair with going into the parks.
Many of us need to book trips many months ahead. I have a hard time believing this schedule change for MK extra Deluxe hours, or the Star Wars Weekends cancellation weren’t known by Disney months before the announcement - they were just delayed to get as many bookings as possible for an experience they knew wouldn’t deliver. Seems to be in line with their current short sighted marketing strategy.
Now that our kids are grown, we just don’t book our DVC reservations around any park activities. We mostly just enjoy the resorts, golfing, and Downtown Disney. If it works out to go into a park while we are there, we might for a day. Before we always bought a ticket to last the length of our stay. But after all, since we are DVC, as Disney told us, ‘we only paid for a room.’