Is it legal to knock out-50 hp in the forehead of the tank as shown in the video? Is this considered a scam?

https://www.youtube.com/watch?v=DLftlLY-lyI

Its a sort of glitch shot but it is not something we ban for. There is a very small point on the top of the tank that seems to allow the shell to fly through and hit the rear hitbox of the tank which does double damage. It takes skill to do consistently