I would guess that they have put a pause on that time because they may not have decided yet whether they will still be operating at reduced capacity. They know that time period has a lot of demand due to the anniversary and it would be a lot of people to deal with if they allowed normal booking and then wanted to scale back. If it were me, I would book something off property with a good cancellation policy, so you have a room somewhere, and then keep checking for on property availability so you can switch if things open up.