The trucks payload is already calculated with a driver and a full tank of fuel.
That "used to be the case" but is no longer the accepted "GVWR-truck weight= payload remaining" calculations...
It's impossible for any vehicle manufacturer to know how much a driver weighs. Used to be, they calculated 150 pounds for driver weight. Some manufacturers included the driver in the curb weight, some didn't...
Today, a "driver" could be a 90 pound "grandma" or a 450 pound "McD's career manager with an obesity issue"... No longer does RAM, GM or Ford calculate the driver in the truck weight then give the payload remaining...
Currently all 4 HD truck manufacturers state to look at the payload sticker, subtract the weight of the driver and all passengers and what's left is the available cargo weight.... The driver is no longer included in vehicle curb weight...
Now, there's still a "loophole" in how all 4 manufacturers address payload. NONE of them, in those calculations state "AND ALL EQUIPMENT INSTALLED AFTER THE TRUCK LEFT THE FACTORY".... So, if an owner installed a cargo bed cover, a crossbed took box, filled it with welding equipment, those things are "still cargo" but the instructions in all 4 owner's manuals no longer address that stuff in the payload remaining examples....
But, bottom line: No longer is the driver's weight considered before calculating payload remaining.....