Now try to explain all this and the importance of RAWR and GCWR and tire load ratings etc. to a sales person. Suddenly you realize they have no idea what they're talking about, just like RV sales people! They just want to make a sale.
Pretty typical of regular vehicle sales folks.
I've put several trucks in commercial service and always deal with a dealer ships commercial sales person(s). The ones I've delt with know if the customer is going to use the truck to pull a 15k or 25k GN trailer then the truck has to have enough rawr/tire load capacity to carry hitch loads safely/legally....and enough engine to do the job and the right drive train to last.
That payload sticker is a GVWR based payload number. Most new folks to the trailering world may use that number to figure a weight for a truck camper or a GN/5th wheel hitch load which may overload the trucks RAWR (the lessor of a wheel/tire/rear spring pack/axle assy).