Mostly, it means the marketers wanted to sell to folks with 1/2 ton trucks.
They generally are a little lighter but that's mostly because they are smaller with fewer slide outs.
The fact they have a hitch on the trailer doesn't mean a lot. 5th wheels are typically limited by the pin weight (not the pulling power). A small utility trailer on the back of the 5th wheel has very little effect on the pin weight (technically it probably pulls 50-100lbs off the pin weight since it pulls down on the back of the 5th wheel). Most 1/2 ton trucks can pull a lot more than they can carry.
