What about this truck manages even transfer of weight to both axles without a WDH?
Short answer: NOTHING.
Long answer: The truck can tolerate having more weight removed from the front wheels partially because it's heavier to begin with, and partially because it has plenty of capacity on the rear axle to handle the trailer's tongue weight, and does not need to distribute the weight to prevent overloading.
The main reason for using a modern WDH with integrated sway control on a heavy duty pickup truck is the sway control. It helps with the push-pull on the highway. It is there as "belt and suspenders" just in case something unknown and unforeseen sets the trailer into a sway event.