This is all correct and has been the case forever with Marriott. While the Marriott rules have always stated the member only gets credit for one room, many of us would get credit at some hotels for the second room. It has widely been speculated that some former SPG hotels would continue giving credit for the second room, too, but there is no way to know which hotels will and which won't.

Several times a year I would travel with salespeople who might have allegiance to a different hotel chain. On night one we might stay at IHG in two rooms, but both registered under the salesperson's account. The next night we would stay at a MR hotel both under my MR#. We would do this because two nights of MR points were more valuable to me than one MR and one IHG, and visa versa for the salesperson. We would run the charges separately under our own cards so as to get separate folios so we could expense the rooms on each or our expense accounts. When the reservations were run separately even though they were each under the same MR# I would usually get credit for both nights. Given I was already LTP and had way more nights than I ever needed the extra night didn't really matter. This was more likely to happen at the lower end brands like FI, SHS, CY, TPS and RI and less likely to happen at the full service hotels, but it did happen at full service hotels.

Nothing was ever audited, clawed back, questioned or seemingly ever noticed.