To those who think the Marriott.com website does not update in real-time to show actual availability, I now have a data point to contradict that. The story I'm about to tell is a little weird and not directly the situation we've been talking about in this thread, but does show that the website updates instantly.

I had booked one night at the Courtyard Manchester (NH) Airport before an early-morning flight in an executive suite--their highest and most expensive category of room. I arrived around 11:00 PM and was checked in by a gentleman whose name tag said that he was the front desk supervisor. He did the usual clicking and clacking on his computer before handing me the keys and telling me that he was happy to upgrade me to a "spa suite". I thought that was a little weird, but headed off to my room.

There were two problems with that room. First, it was just a normal-sized room (as best I could tell) with a Jacuzzi tub in it. Second, it was next to their swimming pool which was being actively used by a group of REALLY loud teenagers. There was no way I was staying in that room under any circumstance.

Without even unpacking I hopped on the Marriott app on my phone. I saw that "spa suites" were actually a room category below what I had booked and was paying for, and that "executive suites" were still available.

I was really polite about it, but I went back to the front desk and saw the same guy who checked me in, and I just told him that while I appreciated his gesture with the "spa suite" that I really just wanted the executive suite I had booked. He clicked and clacked some more and told me that he did have one of those rooms available (what a surprise, I thought...) so he swapped out my key and off I went to a large corner suite far away from the swimming pool.

First thing I did was to hop back on the Marriott app, and sure enough all room types were still showing as available except for the executive suite (so apparently I got the last one). It couldn't have taken me more than a minute or two from being assigned to that room to checking it on-line, so to me that says that Marriott.com is updated in real-time based on actual hotel availability.