Most likely, he was playing with a tank or a plane. You can tell by the number of assists and 0 buildings made.
Edit: I just saw the video. Seems like a bug to me, since once he’s out of AA you were able to kill him. Remember that AA was touched recently, so it’s not uncommon if they screwed up.
I totally agree on the balancing aspect of the game. It should be changed to a PROPER WORKING one, and instead of letting people choose between teams, create an auto fill option for queue. It’ll improve both queue times & player’s balancing.