A slight of hand. They quote the hitch weight as it leaves the factory, empty, in other words. The excuse is they have no idea what the actual hitch weight will be until the owner loads it, since both cargo weight and placement have a dramatic effect. The unethical thing is that they don't warn you, and in most cases don't even mention that is an empty weight, so the uninformed swallow the bait whole! Worse, many sales people use it unreservedly to convince gullible buyers.
In a 5W, the bulk storage area is way up front, and in most floor plans the bedroom and alley storage areas are also forward of the axle. Often at least some of the water tanks too. Pin weight grows quickly, even lightly loaded.