I'm not sure you are using the same definition of tunneling, at least as how I understand it. It's not to practice throwing meatballs down the middle of the plate. The idea is for the ball to be in a tunnel as it travels to the target, then break to whatever the ultimate target is. If done well, it would make pitch identification that much more difficult for the hitter. Some major leaguers use it to great effect.
Can't you just see if the ball is moving? Why the tunnels?