Welcome. Since I'm on the road I can't elaborate much right now, but the short answer is, there is weight distribution, sway control, and the combination of both of them. Some WDHs have sway control, some don't.
With the shorter wheel base and 3500 pound towing capacity of your Pilot, I suggest a WDH that includes sway control. E2 and Equalizer are two brands that do both. I have an E2, and Equalizer owns E2, FYI. I used to own a popup and if I didn't use the sway bar (didn't have WDH then) the thing was nearly impossible to tow no matter the other anti-sway steps I took (see the link in my signature for info on sway control). So in that case it definitely helped. I towed my pod for about 2 years w/o any sway control or weight distribution on our prior TV (tow vehicle) but a good day in wind convinced me to get sway control. Getting the E2 also solved the weight distribution problem. When I changed my TV I tried w/o on one trip and went back to using the WDH sine it improves the ride quality.