I took a flight in F as an UM once. It was great. Compared to an economy seat, it seemed like I was sitting on a couch.
I don't understand why AA is going so overboard with this. It would be one thing if someone in F wanted to switch seats with the passenger next to the UM. But to switch seats with the UM? It's an odd suggestion, but other than that, so what? They may as well interview random people after the flight to see what they're up to.