The human body can do some amazing things, some of it thanks to adrenaline, others thanks to blind luck and how hard it is to hit a moving, reacting, target cleanly.
People have gone into emergency rooms full of cuts, and stabs, some with knives still stuck into them, sometimes in their heads, others have been killed with minimal strikes.
Luck of the draw sometimes.
The video is typical of what a "semi-trained" person will do with a knife, no one ever does what we typically see as demos.
Psalms 144:1
Praise be my Lord my Rock,
He trains my hands for war, my fingers for battle !