This video has probably been around for some time.
Now that it is on Youtube it will no doubt reach a wider audience. As with all true art every viewer brings their own interpretation.
Personally I think it demonstrates a questionable and unnecessary training technique, probably counterproductive.
But I will cheerfully yield to any trainer who can demonstrate otherwise.
As for me, I figure someday most everyone will figure out weapons are not toys, not for relaxation or sport or entertainment, but tools to be treated with utmost respect and caution and have but one purpose: to harm someone before they can harm you.
Horse around with a real live Katana in that fashion and see what happens!