I just had one work in a way different than described here, at least so far. I had a Friends and Family rate booked at the Park Hyatt Siem Reap before I chose my 50 night SUAs earned last year. The concierge said they had to check with the property to apply the SUA, which appears to have been done. The SUA was removed from my account and the reservation on the app indicates the SUA was applied, but the room type is still the base room. On the website there is no indication at all of an SUA upgrade.

I could have just cancelled my existing reservation and booked the whole thing on the app but the rate had gone up.