You have definitely drank the kool-aid. First, the definition of sway is the uncontrollable side to side movement of the trailer. Ever heard of a lever? Do you really believe your (or any other) multi-thousand pound 30 ft lever can be controlled by a device with maybe a couple hundred (probably less) pounds of resistance? On the same vane, if you were to swerve to avoid a moron on wheels or a deer will that same lever be magically controlled by the little resistance of a sway gimmick? Why is it that TTs need sway control and enclosed cargo trailers do not? After all, a TT is nothing more than a cargo trailer with windows and appliances, not to mention cargo trailers are much more likely to be loaded improperly.
I can say with confidence I am an experienced trailer pulling driver. Besides my personal trailers, that I don't keep records on, I have logged several hundred thousand miles towing TTs and enclosed cargo trailers of all shapes and sizes, both new (unloaded) and for private owners (loaded). I don't get to go inside and move stuff around, yet not one of them has resulted in uncontrollable side to side movement. That is because a TT, by design, is very difficult to load incorrectly. I've had flat tires, driven in high wind and encountered moron drivers, not once in need of a sway "control". As a footnote, the first trailer I was assigned when I started transporting was a TT. It was the first one I ever towed. I fussed with the W/D (no sway device) for an hour before I left the yard. I hadn't traveled 5 miles before I was on I84 with a strong, gusting, quartering headwind. Amazingly (by your beliefs) I didn't have any trouble other than lousy fuel mileage.
Consider this. The government has invaded all aspects of our life, including safety requirements for trailers. All ball hitches have to have safety chains in the event the coupler becomes disconnected or the shank of the ball breaks. We all can probably relate to an instance where the chains came into play, so they are a viable safety device. With well over a half million miles towing I've had it happen once, so lets say the odds are 500,000:1 All trailers with brakes are also required to have a safety break away. Trailers with electric brakes have a pull release cable & switch and a battery installed on the trailer. Have you EVER heard of the coupler becoming unhooked AND the chains breaking, which would be needed for the electric break away to be activated. Anyone??? Ever?? Apparently someone in govt has heard of it, so lets say the odds are a billion to one. So, if a sway device is so crucial to safety why doesn't the government require them on all box type trailers???? There is nothing but anecdotal evidence, and the constant repeating of myth, that keeps the sway device manufacturers in business. Even the government has no reason to believe there is a need for them.