“You’re putting evidence on the ball and sending it to the umpire’s neighborhood.”
Supposedly everyone does it but they at least have the brain capacity to be discrete. Being caught once is bad enough but twice in such a short period of time suggests a special level of idiocy.
Th brown spots will show on the rotting ball going up to the plate.
Most batters will notice the discoloration and ask the umpire to check the ball. You see this all the time when a ground ball is hit and the players will flip the ball to the umpire who may take the ball out of plate.
If you outlaw pine tar some pitchers will just cut the ball with their belt buckles. Or the catcher will cut the ball and throw it back to the pitcher.
Always a way.