Hopefully this doesn't give people another reason to try and get by without Squats and Deadlifts.
As tribunaldude pointed out, who knows what he did before 1990. He could have been squatting and deadlifting near 700 for all we know.
And think about how his body has adapted while just using 1 leg!
Think about your 'strong' bodypart. Maybe you played soccer for 10 years, so now your legs grow like weeds when you train them. My upper back is way ahead of everything else, and I think that's largely in part to swimming competitively for 10 years. Athletic history like this, I think, effects how your body responds to stimulus in the weight room.
Taking that into consideration, I'm thinking if swimming and basically doing a unilateral pulldown for 1-2 hours for 10 years has turned my lats and upper back into a bodypart that responds very well to training, then walking on one leg all the time for 18 years must have some effect.
Without knowing anything about this guy other than that he's built a huge leg and he's jacked all over, I'd venture to say that his leg is his easiest bodypart to develop since it's essentially had to adapt into a super-leg in order to meet the demands of day-to-day existence.
What I think is crazy is how thick his erectors are and how there perfectly symmetrical. I guess he must just do crazy heavy back raises or something.