I would assume it was just a redesign of the graphics. Zenith probably wanted their logo more prominent and someone, maybe Felix, decided to add the flag. There was a four month gap between tests and final jump. Maybe Zenith saw the test jump footage and saw their logo got cut off of something. I'm sure they paid a shit ton of money to have it there. Edit: Saw more pictures and there's an Austrian flag on the other side of his name, which is where he was born, maybe the American flag was added because someone exec complained or some bullshit, who knows.