Correct, that is otherwise known as "even squat" and it is old information. On GM trucks there is a bump stop that prevents the front end from going any lower than stock ride height. If you try to get "even squat" you will put so much weight on the front of the truck that you will cause damage.
What is important is the FRONT ride height. When you hitch the trailer, the rear goes down and the front goes UP on your truck.
Previously, the recommendation is to return the front ride height to UNLOADED levels, but no lower than that.
However in the last few years some manufacturers are now saying that you only need to return the front HALFWAY to unloaded ride height.
Ride height measurement is a good way to tell if you have enough weight on your front wheels for proper control and steering. The springs compress/squat so much for a certain weight, and spring compression translates directly to ride height.
For example, if a certain point on your font fender is 31" off the ground unhitched, and 31" off the ground with the trailer hitched and WD engaged, you have roughly the same amount of weight on your front wheels either way.
