Using a fast controlled negative to engage stretch reflex on a maximal bench attempt is a common technique- he is trying to generate power, not 'feel the burn'. If the full 500 was dropping on his chest, he would be squashed like a bug, strong ribcage or not.
I agree that Tank as a fighter is under rated. He has often said in interviews that the only problem with his 'image' is that people forget that he trains damn hard and is not just some clueless brawler.
The fact that he gets beaten by the cream of todays generation means squat. So does Royce (without putting up as much of a fight). They both lack balance. Tank is all striking, with weak grappling, Royce all ground with the stand up game of a 5 year old in a playground. One is criticised as shallow and one dimensional. The other is hailed as the father of modern MMA. Go figure