Could be a myriad of things, including no sway, just regular trailer wiggle.
My 32' cargo trailer, akin to about a 30' lightweight TT, no wdh, no sway control, does wiggle around at highway speeds, say, over 65mph. It's not sway, trailer appears to track straight in the mirrors and if I just let it "wiggle" rather than try to correct each sensation, I run straight down the road.
That's the first scenario.
Next is proper setup of your wdh and suspension. You shouldn't "need" sway control if you're set up right. IMO sway control is there to help setups that aren't right. Ie, truck overloaded to point that the trailer is driving it due to way too much tongue weight or the opposite, too little tongue weight, allowing the trailer to drift around rather than be planted on the hitch ball.
I'd first make sure you have acceptable tongue weight.
Then make a run "naked", no wdh and just enough air to keep the truck about level (if needed). You should pull straight if there's 700-1000lbs on the tongue.
Now adjust the wdh to transfer a little weight forward if the steering feels floaty and unloaded. May need to dump some air as you unload the rear.