There is a difference between "No Blackout Dates" and "Last Room Available". "No Blackout Dates" means that hotels have to provide at least a few rooms every night of the year for award reservations. IOW, they can't completely blackout a particular date. But there is no requirement to provide ALL their standard rooms for awards.

Starwood's program would be an example of a "Last Room Available" program. As long as the hotel has "standard" rooms available for sell, then they must also provide them for awards. Thus it is much easier to find award room available with Starwood hotels for "special" nights like New Years, etc.