Any trailer can sway, and most can cause bad control problems when they do, even to a much heavier vehicle pulling them, and TT’s are the worst… controlling sway comes from balance, and being able to maintain the balance… RV’s are not balanced side to side and often tongue weight is hard to control, and not well controlled when in motion because the axles are most often at their extreme forward position, especially done for allowing smaller trucks to pull them… WD hitches and sway control becomes much more important for RV’ because of their (poor) design…
even the flat bed with the backhoe loaded may have a high center of gravity but the weight causing the high center of gravity is carried and better centered between the tires… load control is far better and easier in a utility or on flatbed trailer… heavier loads are carried on heavier frames to be pulled by heavier trucks instead of moving the axles a inch or two forward to allow for a undersized truck to haul it…
you could go thousands of miles and not need either the WD or sway control, and when just the right conditions present themselves a catastrophic event can happen before you are even able to react to it…
any bumper loading offloads and reduces steering control to some degree and makes the TV over-steer more pronounced in reactive steering situations… a dump truck with a flat bed trailer and backhoe has a heavy load carrying hitch with the hook/ball right at the rear axle causing less steering axle off loading…
wind causes sway through instability, because the wind suddenly changes the trailers loading destabilizing it and speed and inertia takes over from there…