It is entirely possible that the rate will be honored or that it will not be honored. Anecdotes from some other property or some other rate will not help you. Thus, you have two choices:
1. Book and see what happens. Be prepared to pay a lot more at any time up to and including check in.
2. Call the property (not reservations) and see if it will honor the rate or give you some other roughly equivalent discount.

Bear in mind that while many properties are struggling, one way they are mitigating the damage is to close of floors, wings and the like. Thus, whether a property is "booked full" by the time you check in may only means that the 20% which it operates at are full.