Originally Posted by TXFolkie
As I read my manual, automatic sway control provides differential brake control to your tow vehicle but not to the trailer. It does also apply the trailer brakes but evenly on both sides. The brake control wiring to the trailer doesn't have a left/right so there's no way to accomplish differential braking as needed to the trailer for sway control. Always use your hitch sway control to prevent or minimize sway. Then, if all else fails, you can rely on your vehicle sway control to hopefully keep the shiny side up.
You are correct, in that (so far) trailers do not have multiple braking channels to apply voltage to individual brakes independently.
But you don't need differential trailer braking to control sway. As far as I know, since the beginning of trailering with the oldest turd of a time-delay brake controller, trailer sway was halted by simply applying the trailer brakes manually (single-channel, to all trailer brakes). This simple act brings the trailer back in line.
The only difference here is that (apparently) some/most/all integrated systems will do this for you automatically at some point.
That said, I agree with everyone here. Don't rely on the electronic nanny for sway prevention. This could result in overheated trailer brakes from constant use. If you don't have sway control integrated into your WDH, let a cheap friction sway controller keep the trailer in line 99% of the time, and the electrical stuff will help further if/when needed.