I agree, unfortunately, the FAA doesn't view us as one airline. Quite the same as Comair and Delta. Though they operate pretty much as one airline from the customers perspective, they are, indeed, two different airlines. Both are subject to the interpretation of the rules of each airlines individual FAA Cabin Safety Inspector. So, there are differences in the rules as they pertain to the cabin and the passengers, although they may not be glaringly obvious differences to the passenger as with this headphone thing.

For a long time, Southwest Airlines FA's were allowed to leave the aircraft during boarding/deplaning as their FAA Cabin Safety Inspector believed that their pilots could evacuate an airplane in the FA's absence. No other airline had that exemption and, unless you had more than minimum crew on board, FA's at every other airline were prohibited from stepping off the airplane while passengers were on board. It's differences like these that make it confusing for our customers.