Data point: I booked a 6-night stay in my name for myself and my wife and a 4-night stay in my name as well for my mother-in-law (she arrived 2 days after us). I got points and nights for my 6 days but no points or nights for my second room. They offered to give me points for both rooms for just the last 4 nights, but that would involve losing 2 elite night credits (as the first 2 days of my stay would be thrown out entirely).