you sir are correct...the math just doesnt add up....
i feel so left up maybe i should put up my stats too...
6'
300lbs
12%
national qualified competetior
405 for 8 on bench
405 for 6 on front squats
600+ for 6 on deads
but i cant curl 80's not even fukin close...hell last week i got the 70's for 5 a side and my form was ok at best, so at 80's i would look horendous...not saying you cant but if you look at the quote i highlighted above something just doesnt add up bro...
as for your why do big guys lift light weight??? well first, who gives a fuk...seriously...second...i do a lot of work with light weights for lots of reasons...i dont wanna get hurt, i am at the end of my work out, i like to mix up all my workouts and confuse my body, im fukin lazy sometimes

, some muscles are built better doing high reps and light weight i aint gonna do tricep kickbacks with the 80's, maybe i am competing soon so i am trying to focus on definition....hope this answers why some big guys do it....i would love Pinnacle to come in here and answer this...he might get banned though...hahahaha...
just do what works for you and dont fukin worry about what anyone else is doing, it aint gonna help you one bit....