I don't book basic super often... but tonight when I scanned my back of the bus BP, it spit out a new seat, an aisle C+. That was a first for me as an elite. It's a bit unclear how and when you can change seats, because my first flight of the day the entire main cabin was greyed out (every seat was either occupied or blocked) and then right before departure a few seats became selectable and then loads were maybe 50% so I have no idea what the seat map was showing. I was the only person in my whole row (GEG-ATL).