Discussing what "should" or "could" or "might" happen is educational (in the same way that ghost stories around a campfire are educational). Does anyone have any actual experience with what actually DOES happen? Has anyone on this board had their rate changed at check-in? Tell us about it.
I have 30 years experience as a road warrior, traveling almost every week.
IME Hyatt is very lenient.
On occasions, I have had a "guaranteed for late arrival" reservation, and I phoned the hotel to tell them that my flight was cancelled and I would not be there. I acknowledge that the room was guaranteed, but I also explain that I'm calling because I want them to be able to sell the room if needed, because it's a natural fact that I won't be there. I've never been charged for any reservation when the flight makes me no-show.
I've showed up very late at a hotel and all they had were smoking rooms. I chose not to stay there, and was not charged any kind of fee (even though the reservation was "guaranteed").
On exactly one occasion, I showed up at a hotel in Charlotte NC, checked in, etc. I was a bit miffed because they didn't seem to have any record of my reservation. A few days later, I discovered that a nearby hotel charged me for being a no-show. (I had gone to the wrong hotel : the two hotels were near each other). Hyatt reversed the charges for the second (unoccupied) room.
I've been asked to show my corporate ID exactly one time, at an Avis rent-car counter in Montreal.
Your Mileage May Vary.