Clear hacking. You cannot move that quick as an exploit.
You're right, it's not a hack because he's not interfering or manipulating game code to his benefit. It is however a clear exploit, as it creates an advantage that cannot be countered by using game design/mechanics in a way that was not intended. You are not meant to move or shoot through those shields. Doing so in order to prevent the opposing team from lowering the shields while you yourself cannot be targeted or stopped from denying the objective is not a clever use of game mechanics. Arguing over semantics is simply a sad attempt to rationalize cheating.
Actually, it is a hack. Look closely next time before you comment. only one player is moving faster then they should. It is not an exploit