True, but you certainly would know if you kept your hands above the ball.
I've truly never seen a swing on a strike where the hitter's hands were below the ball. Maybe you meant the barrel above the ball? I've also never seen a hitter swing where his hands actually traveled outside the path of the ball. "keep your hands inside the ball" is a pointless comment because every hitter actually does this each and every swing they take. If the hitter's hands ever travel outside the path of the ball, the hitter would hit the ball with his forearm or something. We as coaches need to make sure that the players really understand what we say by saying what we actually mean. "Keep the barrel inside the ball" and "keep your barrel above the ball" might be easier understood by all.
Barrel to ball relationship is what ultimately matters no matter what type of pitch you are trying to hit.