I'm not sure what you are trying to say, but as best I can understand, this does not match my experiences.

Per Marriott Bonvoy's T&Cs, a person can receive points for upto 3 rooms per night, but receive night/stay credits for only one room per night (there is no rule that states they have to be at the same hotel.) I've had a few situations similar to Sooks' where I was staying for a month or more at one hotel while still traveling for a night or 2 elsewhere. For me, every time that happened, I actually received both points and night/stay credits from both hotels even though some (or all) the nights overlapped. I suspect that Marriott's IT system wasn't really designed to track multiple stays at different hotels and give night/stay credits for only one of those stays. But I haven't had this scenario in a few years (changed jobs where I didn't have to be at one location for long periods of time). So it is possible that Marriott's system might possibly catch the overlapping stays at different hotels now. If that were to happen, you should still receive points for both stays, but per the rules only receive one night credit per night.

If you decide to have overlapping nights at different Marriott hotels, my suggestion would be to plan for and expect points for both rooms but only one night/stay credit per overlapping nights. And consider it a bonus if you were to still receive multiple night credits.