Legal for what purpose?
For registration, you typically register the vehicle for whatever weight you want to pay for. It does not have to match either the placard on the door frame or the “Consumer information.”
The “Consumer Information” sheet is just information. You don’t have to have a truck camper as heavy as the sheet permits; the camper listed is chosen to allow you ample cushion for an unspecified number of passengers and miscellaneous “stuff.” You are free to make other compromises if you wish.
For driving down the road, you can load your truck as heavy or as light as you wish. Doesn’t matter if it’s a truck camper in your box or a load of gravel. You may get fined if you’re exceeding what you paid for on your registration, but usually not for exceeding the placard weight.
Many trucks are not even titled with the actual weight, the title for mine when I bought it stated a GVWR that was less than the empty curb weight of the truck!
Additionally, on my truck, the placard weight is stated conditionally, i.e., “with this particular tire combination, the GVWR is X.”