I was #1 with FC full an hour before boarding, same at half hour, same at boarding, still #1 after I boarded as well as when they moved the guy up. My gut says that the guy was a non-rev/employee as he had been chatting up the GA before the flight. Most likely someone missed their connection and they bumped up him instead of me...

Also, the total number of people on the UG waitlist remained at 20, both before and after they moved him. The guy was dressed casually and did not have a "pilot"-type roller case.