I must have gotten really lucky then. As part of an F redemption on LH, we booked a flight LAX-YVR on AC. There was only 1 seat available each in Y and C, so we took those two. Then, about two months later, I checked KVS (well, I checked it every day, but that's when it happened), and that flight had another C seat open up. I looked earlier, and no one had picked a seat in C (thus, presumably, no one had made a redemption before we did), and the agent said that AC often releases only one seat in each class. Not that I would have cared that much about being in the back of the bus from LAX-YVR, but it's certainly nicer to be up front if you've paid the redemption amount for F to begin with.