I'm being told the 4pm is only for "available room categories" (i.e. not suites), but this is not spelled out anywhere in the Bonvoy guidelines. My understanding is it's a guarantee except at the specific resort/convention properties. Does anybody know if there is an exclusion of this nature documented anywhere? For this stay I actually am using SNAs to upgrade a standard room, but that's happened in the past too, and the 4pm guaranteed checkout was always honored.