So am I that he finally told a truism. While in boot camp, I watched some poor guy in formation fall directly on his face and broke his jaw and cheek bone. It was determined later by witnesses that he had locked his knees. To this day, I always relax my legs while in the shower or standing for any length of time.
I learned that while I was in video production. Running camera at a meeting all day long, you have to unlock your knees, or look out below!