You're correct, mostly. Rezzies provide more than just cooling on ATV shocks. They separate the oil from the nitrogen, disallowing emulsification. It keeps the oil viscosity the same no matter how long you ride. With smooth body, or non res shocks, you mix the nitrogen and oil together, causing foaming, and varying degrees of dampening and rebound. So as you ride, you are actually mixing air into the oil, and more or less creating foam, rather than a steady oil consistency. I'm working on a design right now to convert standard non-res shocks, and integrate a dividing piston into the bodies. Fox, bilstein, king, and swayaway, along with other offroad shock manufacturers have been doing it for years, but for some reason ATV shock builders haven't caught on.