It seemed a little odd that the OP had called in Nov to confirm seat assignments on flights in Feb. Anything could have (and did) happened in 3 months. The smarter thing would have been a call a few days prior to departure to confirm seat assignments. While this can be inconvenient to some, it's worth the time avoid what happened to the OP (middle seat in the back). I would imagine this could have happened to other carriers outside of *A. Ideally, traveling on itineraries involving partners should run as smoothly as if it were on a single carrier, but it doesn't always happen, be it *A or not.

LAX