The airline accommodated you pretty nicely as the day went along. AirTran employees seem to have more ability to give a favor, and make bad decisions as well, based on their own discretion.
The practice of flights leaving early is still a real annoyance to this frequent flyer, however. The problem gets worse at the start and end of the day.
The UK regulator of passenger rail franchisees severely penalizes early departures in their on-time studies.