"The Downwind Turn".
The man is clearly a fool. If the downwind turn was so deadly I would be dead many thousands of times over.
And to some it might be deadly, if susceptible to disorientation.
I would like to see his take on loading it to a knife edge, right to the region of reversed command. Lose a knot and you are going down. Any turn other than into wind would bring you unstuck, if his theory is correct.