Yes, I do not understand either... I asked one of the reps at NSA about the Winnebago warning about not using surge braking and this is what he wrote back:
"The ReadyBrute Elite cannot connect to a ball hitch, it requires a 2" receiver. This is the first time we've seen any recommendation referring to a surge style braking device and it makes us wonder why they didn't recommend against towing at all then. If you use a tow bar, tow dolly, trailer, etc. they all place stress on the hitch. A surge style brake would place the same stress on the hitch except since it has a shock and spring it actually takes away a lot of the forces applied from the weight of the towed product pushing and pulling on the hitch. Roadmaster makes a tow bar with shocks in the legs to "make the ride smoother". So this doesn't really make sense to us. Trailers have been using surge brakes for many years before us and now our ReadyBrake will be 20 years old next year. If there were problems from using a surge brake it would have been widely known by now. Most trailers connect with a ball hitch too.
We are not asking for you to go against your manufacturers recommendations and feel that you should use your own judgment."
So, I go back and forth about getting the ReadyBruteElite and the RVIBrake2. All in all, seems the ReadyBruteElite would be the easiest install.