The installation instructions provided by most WDH manufacturers are woefully out of date and/or woefully inadequate when it comes to whether the tow vehicle should be loaded as for camping.
Eaz-lift have been selling WDHs since the early 1950s and their installation instructions seem to be written for "cars" to which they refer several times.
Eaz-lift states: "Measure towing vehicle before adding load to towing vehicle."
Equal-I-zer (whom I consider to have the most up to date instructions) is much more specific: "While installing or adjusting the hitch, the tow vehicle and trailer should be loaded just as they will be while traveling. This includes full propane and fresh water tanks, and any other cargo (passengers & gear) the tow vehicle or trailer will carry, including ATVs for toy haulers."
Equal-I-zer was the first WDH manufacturer to abandon the "equal squat" approach toward WDH adjustment.
IMO, the WDH should NOT be used to compensate for any of the load carried in the TV.
Also, most major TV and WDH manufacturers now specify that the WDH should NOT be adjusted to make the TV "level".
Instead, they specify that the front end height, with TV attached and WD applied, should never be less than the unhitched height.
Some manufacturers specify that only 50% of the front-end rise should be eliminated, and some specify a range of 50-100%.
Ron