I'd write the letter, but not sure you're due anything in return. I don't think your parent asked in the correct way. They weren't put on the standby list, they were confirmed onto the flight. The person in TPE (and I agree, I would have told them to wait till SFO) saw this is as a change in routing, not a standby request. They are not familiar with standby as it occurs regularly with the domestic (and transborder, etc) routes here, they don't ever see them.