Ever driven up or down a somewhat steep change in incline with a WDH? I have. The back wheels come off the ground and it's SUPER sketchy. Luckily that was just a drive way and I was headed downhill anyways.
The proper way to set something up is to load directly above the rear axle and put the full tongue weight on that axle, like how a gooseneck does. Loading a trailer at the rear hitch actually takes weight OFF the front end of the truck, though if you have it leveled correctly with support bags, the change is minimal, even for maximum tongue weights.
Weight applied over the rear axle is considered payload, it is not tongue weight anymore.
In bed hitches(gooseneck, fifth-wheels) when installed properly are forward of the rear axle which changes the physics of how the weight of the trailer affects your truck.
Bumper towed trailers apply tongue weight which is behind the rear axle. WDH "move" the tongue weight forward to load weight on the front wheels. They not only help with the sag but if any hard breaking is required keep the trailer from using the rear axle as a fulcrum. When you brake hard with any vehicle, the front of the vehicle dives as the inertia loads the front wheels, a trailer will do the same thing only it is pushing down on the back of the vehicle. Given the hitch point is about 3 feet behind the rear wheels, it will act like a giant lever without a WDH. With those physics applied, the front end goes light.
The correct way to set up a WDH is to run the truck and trailer over scales to see where the weight is.
Odds are if a WDH lifted your back wheels off the ground, it was probably set way too nose heavy or the trailer suffer damage from bottoming due to the massive indifference in the elevation. A situation like you described would not happen on the roads while your traveling. If tight maneuvering is required, it takes all of two minutes to release the WDH.
