When you put the set together, you get a better feel for the design. Think of the lower cushion as two planes separated by springs. There is the plane that supports the lower cushion and the upper plane which you sit on. The seat back is fastened to the upper plane so that when the springs compress, the back moves up and down with it. In essence, when you sink in to the lower cushion, the back follows. On a normal seat, you sink into the lower cushion while the back remains stationary essentially rubbing up and down on your back with every bounce. It really doesn't sound like much until you experience that seat. Then it will all be clear. In my mind, the vent is "fluff".
