http://news.pickuptrucks.com/2014/07/more-game-playing-now-gm-fesses-up.html Not surprising. Ram will probably next. Or maybe not. Time for another standard for payload ratings.
Even 50 lbs, if it gets them greater rating than the other guys, gives them temporary "bragging rights". That say "highest rating in its class", not "we beat the other guys by 10 lbs".