Just got off the phone with the PM rep. She said she had absolutely no idea why it was changed. It changed a day after my booking and the only note on the change was "QTF" which she said she hasn't seen before. Usually they see an explanation for all changes. The only thing she could think of was that I was bumped out of the seat due to a special passenger needing the seat. She didn't elaborate on what constituted a special passenger, but I am sure several things fall into that category including Air Marshals, etc...

She said she would have someone look into it, but overall sounded surprised and confused by the situation.