Japanese guys at the gym – Tons of weight, ZERO range of motion.

Anyone else see this? About 1/4 of the guys at my gym lift like this. They load up the machine or free weights, and just bounce the weight a couple inches for like 10 – 20 reps. I don’t remember seeing this in the USA so much. Then they pound their legs between sets with their fists. Do they know something I don’t?