I've always found the way he talks about "world-class" and "bulletproof" knees to be pretty off-putting. These are nonsense terms with nothing but anecdata to back the claims
He actually has objective definitions for world class: can perform a certain range of movement with a certain strength. Bulletproof is just another term for robustness or avoiding injury and here he sometimes refers to studies on injury.
What is the point of an objective definition if its subjectively determined by one person? Who is he to decide what is world-class and what isn't?
And for "bulletproof", I know what it means. It's, again, just another subjective term he throws around carelessly. Something bulletproof is something near indestructuble. Does he guarantee no injuries for life if you complete the course?