It doesn't appear that is in the plan; they've instead beefed up the frame and have a custom axle.
That may make it handle better, but neither of those changes modify the GVWR or load capacity. Upfitter changes can decrease the factory GVWR but there is no way to increase it once it leaves the factory.
(Technically adding plates to the frame or trussing the axle will make the truck heavier, which will effectively decrease the payload capacity.)
I'm not saying that you can't modify a vehicle to run better overweight (I had an 18,500 pound Fuso expedition vehicle on a 14,000 pound chassis), but it is still overweight with all the potential liability that comes with it.