I saw a character (Aaron Thunderblade) who had the commander badge. When I examined him he had 9999 wins in first, second, third, and fourth places for pet races. He did not have a pet derby rating. He also had a blank pvp rating. Is this a bug?
No, when you inspect another Wizard, the information is looked up on the game servers. If there is a delay getting that information back and forth (perhaps due to a high population in the game) it will show 'placeholder' information.
This placeholder information is what you most likely saw, young Wizard.