Most 1/2 ton 5th wheels are rated '1/2 ton towable' based on their GVW. If they used the 20% pin weight based on the GVW most would not be 1/2 ton towable.
It's not always a 1/2 ton issue, it's really just not understanding payload ratings. 1/2 tons are more limited to the trucks GVW and tied more closely to their payload ratings because the RAWR is usually maxed when the truck hits the GVW. Very little fudge factor like 3/4-1 tons.
It's the marketing factor that is giving 1/2 ton owners a false sense of buyers delight. You don't see 3/4 ton towable on 5'ers. When 1/2 ton buyers see the '1/2 ton towable' sticker and then hear a salesman's '1/2 ton towable' sales pitch, well for newbies it's 'fish on'.
