OK, obviously it is only a Silver elite promo. so for once being not so elite paid off. I asked Marriott via email to enroll me. Got an interesting response. They can't enroll me anymore, however, their supervisor will manually look at my account around Sept 15 and give me the double points I would be due if I actually had enrolled.

I do appreciate the gesture, and converted a future stay from Hilton to Marriott because of it, so at least in my case it won them some business.