GVWR is a federally controlled safety rating and is computed using solid engineering data. They do not have an option for HOW the GVWR is computed they can only build the truck stronger to gain extra load carrying ability. Building them stronger would certainly cost more money. NOTE that one of the FEW items that is always found on the DOT Safety Plate is the GVWR and GAWR. SOMETIMES they add empty weight (curb weight) or payload figures (which is ialways GVWR subtracted from the actual weight).
Good luck / Skip