Although i have no doubt the knife is very sharp, it looks like that wood is balsa wood, which is very soft and could probably be cut with a butter knife.
Okay I get he's experienced, but you don't teach people how to do this by using a razor sharp precision blade and cutting straight towards yourself. People with no experience will try it, not understand how much pressure is needed, and cut straight into their hands.
Just gonna drop in and say this is Ernest Warther. He was a woodworker in Dover, Ohio, and his family still owns a handmade knives company. His old house has been made into a museum to his woodworking (which is ******* excellent by the way) and the tour guides all know how to make these. I had one for a while, it was pretty rad