This would be more akin to the guy plunking the runner with a new ball while he was rounding the bases. It's outside the frame of competition, sort of like Charles Martin knocking Jim McMahon out of the game, body slamming him several seconds after a pass. There are all sorts of opportunities for misadventures during play (hitting a batter, spiking a fielder, etc.), but when you do something completely out of the realm of the game, it usually gets punished more severely.