TLDR - Is the ticket purchase cutoff (at the airport) for a flight 1 hour before takeoff? I think I was overcharged $71.

Bought my first walk-up fare today for AA 6024 (4:10PM). I tried to do it over the phone at 3PM, but the agent said I had to go to the airport, since it was within 2 hours. I got to the airport at 3:25PM, and the agent quoted a 1 hour cutoff rule. Instead, the agent said I had to buy a ticket for AA 6025 (5:40PM) and standby for 6024. The fare was $71 more. I had plenty of time to go through security and clear the standby list for 6024, which I ended up taking.

I'm skeptical of this 1 hour cutoff, since it's not written anywhere, the AA app was presenting a fare to me available for airport purchase at 3:26PM, and the OP of this thread was able to purchase a ticket ~45 mins before takeoff. Do I have grounds to request a refund?

Screenshot of the available fare on the app: