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
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?
In my experience the best experts are humble.