Do you honestly think that these guys just train their lower legs but not their upper legs. These guys are in shape, upper legs and all.
No! I try not to presume, it's rather more probable that most of them train legs as well.
I want to raise the question of why it is mandatory (is it?) to wear long shorts and thereby hiding a big part of what we usually call a physique. I just find it peculiar that it's called "Men's physique". Why not an honest name, like "Best Beach Boy Body"..
Theoretically it could be match sticks under the shorts of the winner, so are you supposed to imagine or are the legs not part of a physique? What are they communicating with this?