Other than the previously mentioned commuter flights, I never pay any attention to the announcements. If I'm on a mid-afternoon PHX to DFW or SAT, I just walk up after an extended pause after the gate agent calls for F. They've never turned me away; wait for the 8 or 12 F pas to walk on and follow right behind them before the agent calls for Group 1.

Post the results of your letter. Seems like, at the very least, they should offer an explaination on their procedure.