What I am saying is that if you have a determined person attacking with a knife you do not want to do this. In other words it can work in demonstration with a student who is not really trying to counter it but will not work out in the real world. Now you can learn some important sensitivity from practicing like this and that could help you out in the moment but when taken in context and continuous movement without moving to serious control or finalizations (ie. finishing moves) it is just a neat trick!