I understand your concern as it was mine also, so I did my own test. I hooked up the old Outback and done some measuring just to see what happens back there. I set everything in a nice straight line and marked the position of everything. What I found was this, center to center at the head where the spring bars pivot is 6".
My U-bolts were at 30" from the center of the ball coupler back on the draw bars.
Turning the truck as sharp as possible, left or right, the U-bolt moved anywhere from 27 1/2" to 32 1/2". That ring on the end of the strap, top to bottom, is 3". If you watch while its being turned it will control the spring bar through the entire turn. You can see the spring bars being pulled up as you turn and thats where I believe the sway control comes in to play. The extra tension forces the spring bar back into position.