I also think they "switch" processes....the the front desk CMs sometimes exercise control that isn't part of the system:
i.e. You get a preassigned room you don't like. The front desk CM looks into the system and moves someone else who hasn't arrived yet from their preassigned room and sticks you into it. (This happened to us, though I didn't recognize it at the time - I commented on the check in taking so many steps and he said "oh, that's because I'm moving you closer to the elevators." - we ended up in a HC room - so I think he took one look at us and labeled us "suckers." Or perhaps he honestly thought we'd be happier closer to the elevators. We didn't mind the HC room - and it was close to the elevators.) The problem being that the person who was originally pre-assigned that room may end up without their requests being met.
or
They are operating on room ready. They have two rooms available, but the guest doesn't want either room. Rather than saying "sorry, this is what we have currently" they "block" a room that they expect to be available later in the day.
i.e. You get a preassigned room you don't like. The front desk CM looks into the system and moves someone else who hasn't arrived yet from their preassigned room and sticks you into it. (This happened to us, though I didn't recognize it at the time - I commented on the check in taking so many steps and he said "oh, that's because I'm moving you closer to the elevators." - we ended up in a HC room - so I think he took one look at us and labeled us "suckers." Or perhaps he honestly thought we'd be happier closer to the elevators. We didn't mind the HC room - and it was close to the elevators.) The problem being that the person who was originally pre-assigned that room may end up without their requests being met.
or
They are operating on room ready. They have two rooms available, but the guest doesn't want either room. Rather than saying "sorry, this is what we have currently" they "block" a room that they expect to be available later in the day.