How do you know the middle next to you (6B) is being used for seating? By calling and asking? Or, by making a dummy-reservation and looking at the seatmap?
The only thing I do is look at the seat map when I select my seat. If I notice that the seat next to me is available and then after reserving my seat the middle seat has suddenly become blocked with an "X"...then I know it's been "Premier Seating" blocked.
I've never had it not block the seat (if still available, of course) if I'm logged into united.com with my 1K number. It's automatic, in my experiences.
But I'm fairly certain you could call Reservations and inquire if the seat next to you is blocked, if you wanted to.
Middle seat blocking is only a courtesy block. At anytime, the middle seat can be filled.
Correct. Releases are
not only done by airport personnel. If the Premier Seating is full of window and aisle Premiers, Reservations will start putting any other Premiers that request Premier Seating into those middle seats upon request at any time in advance of the flight date.