xD
indeed, you are absolutely correct, but, your head, elbow, and most areas you generally land on don't have enough flesh coverage to make the theory practical xP
which, is why I used the example of palm vs elbow
Anyhow, back when I was on my robotics team in high school, a guy lost the upper portion of a finger to a stationary grinding wheel, not fun. they never let us use the grinder again after that
Another guy I know, lost a large chunk of his leg to a milling machine/lathe (probably lathe, I forget now) when the workpiece got loose, and he was sitting down, and couldn't get away from the machine fast enough.