I think the guy's just building strength, not wrecking his hands, though. I know what you mean about saving your hands, but I just don't think it's unsafe for the average person to build up their hand strength. The hands may be one of the most fragile parts of a person's body, but people are made of some
in' tough stuff.
Like others've said, the sore hands-feeling is normal when you first start here, and that's because many new workers are actively strengthening their hands (and obviously the rest of their bodies) when they move packages for UPS for a living. It goes away because your body toughens to a point where it can handle the daily stress.
Sure, injuries are likely and it's common sense to work safe, I just, again, don't think that the OPs sore hands is evidence or a result of unsafe working. Dude's just gotta work on his death grip.