I wouldn't be too hard on anyone who reads Marriotts "Program Enhancement" notices and comes away misunderstanding this point. Remember, they are making changes to bring their program more closely aligned with their competitors, like SPG. And SPG does talk about having No Blackout dates AND they include the 'last standard room available at all times' verbage.

Basically, I'm thinking that Marriott wants people to make this mistake. They will jump over, and then have their foot in the door with Marriott. By the time they find out otherwise, they probably will have put in a lot of effort, nights/stays at Marriotts and won't want to lose that. IOW, they will stay with Marriott even though it wasn't what they originally thought.