I've never understood Marriotts guarantee. The hotel cheats the guest's benefits, the guest then is supposed to complain to the very people who are trying to cheat/ deny benefits.
The system/policy makes no sense. Why should you be forced to complain to the very people who are breaking the rules? This happened to me at a JW Grosvenor in London. I complained and the manager came and said they would give me welcome points. When I said they are supposed to offer me a choice, they said they'd just give the points as welcome amenity.
If I wanted to complain, I'd have to complain to the very person who was denying me a choice and said they'd give me the handful of points. That's when I knew there was something wrong with Marriott. One of my last paid stays at a marriott