I've had I happen once in 7+ years as a platinum. Flying back to SAN through DFW around New Year's. Y was full and my wife and I were in exit rows, but I didn't request an upgrade as I didn't want/have 6 stickers to burn. I got a call up to the gate and the GA gave me a new BP for F. I mentioned that my wife wouldn't appreciate it if I took that seat and left her in Y. She asked if the companion in my PNR was my wife (different last name) and I said yes. She printed her a new BP for F as well.

All was good until I got home and noticed that 3 stickers were taken from my account. I had to call AA CS and they confirmed the upgrades were op-ups and refunded the stickers.

By the way, the 1 op-up matches the number of times it has happened on both BA (LHR-MUC) and CX (TPE-HKG J->F), so I wouldn't hold my breath for the "free" upgrade on AA.