If you have HID lights
then the car / truck must have automatic correction for sag from weight
on the rear end.
Most newer cars with HID lighting
have a shutter that moves to "level" the lights
and change from high to low.
I know that my 2012 Touareg has this feature.
WDH might be necessary if this is not on your car/truck. If not and the lights
end up higher with the load then while it might not bother YOU it is a clear indication that the front end is lifted and the rear is lower.
Probably, most of the time, under most conditions the light
front end would not cause problems, however all it takes is one time...