Yep, you are probably 100% wrong. Disney does not hold back rooms. They want resorts booked & deposits paid. They won’t gamble on turning away a customer who may not change to a Disney resort from offsite later. If they have a room open & you want to book, you can.
Pop warner does indeed take a huge chunk of the value & moderate resort rooms. Every year. In addition, last years
free dining bounceback promo included dates starting Dec 6th. And the room discount bounceback that has been in effect since October also included these dates. Many people booked early December in anticipation of Galaxy’s Edge opening then, before the actual date was announced. Those people may be staying put in December. There are not even many deluxe rooms available then either. For example, Yacht Club is also completely sold out for most of that week. And has been for quite awhile.
In addition to all that, Thanksgiving is late this year, meaning there is 1 less week between Thanksgiving & Christmas. So everyone who wants to go between those 2 holidays really only have 3 full weeks to visit. That in itself can have a huge impact on resort bookings. Early December bookings have been increasing for years. This year just seems worse than normal.