Wow, thanks for all of the detailed info!! I had no idea that such situations could promt an ARC stock ticket. I suppose either (a) there was something going on in the background that I wasn't aware of (e.g. record mismatch), or (b) AS simply decided to be fancy that day.

I still plan to ask the gate agents next time I fly through OAK. I'll keep you posted if I find out any additional info.