He accepted, thought about it, then went directly to the airline staff for help. They basically told him to phone/web/email and ignored him.
The kiosk was one of those touchscreen things so nobody to ask when he was making the mistake.
It is ultimately his mistake, but at the same time, they're keeping >$40 he accidentally spent so he could board an aircraft 3 minutes early. It's kind of silly.
My read is that he probably screwed up and could've asked more questions at the kiosk. In addition, you're a supportive BIL!