Tough crowd for sure... I think the GA was wrong to improperly set expectations with the OP, and the OP did his part to make sure he'd still be eligible to be on the flight.

AA may have been better off holding the F seat until the very last minute, then releasing it to another customer by doing an on-board upgrade instead. When the OP explained this to the original GA who assured him it'd be okay, the GA brushed it off and didn't even seem to care. How is this good customer service?

Everyone makes mistakes. Sheesh. Lighten up, people.