Like someone said, guys who use heavy weights have a kind of physique and thickness others dont have...(Johnnie , Banch, Ronnie, etc)
And lets get real people...people who use light weights and have great physiques (for a pro a least) HAVE to be genetic beasts....like Flex Wheeler for instance or maybe Gunter, and even those guys put some big numbers a lot of times...
Jay may not force himself 100% to beat his records on weight, but he dont use 'girlie' weights either...he do go heavy, and after all, he is more of a 'volume' guy...And even the fact he do not use perfect form may be a thing that prevent him from injuries (just look at Dorian...Perfect form with lots of intensity led him to what???)
Ronnie may have his injuries but have in mind the guy has like 15, 20 YEARS of heavy trainning...its not like he have a tear every year....
Inhuman volume may work a lot for some guys (lee for instance, or maybe Milos?) and prevent him to have injuries...but this doesnt look to work for anyone....