The loss of efficiency with a gasoline engine is caused by the need to have a stochiometric balance between air and fuell. So when you want to run at none full throttle, you cannot fill the entire cilinder with air. To reduce the inflow of air, a "normal" car just closes down the air inflow over the entire inlet stroke down. The gasoline paradox is: less output == more losses!
Assume you're half throttle, the cilinder only receives a half doses of air by "choking" the inlet, generating an underpressure of 0,5 bar over the entire inlet stroke down. Valvetronic allows 0 bar underpressure for the first half of the strokedown, and then closes entirely the inlet valve, building the underpressure from 0 uptil 0,5 at the end of the inlet stroke. This way the losses are divided by 4! Since the average underpressure during inlet stroke is only 0,125bar!
Cilinder shut down, avoids that the active part of the engine is running in comfort zone where the pump losses are unacceptable high. Each of the active 4 cilinders will receive double the air inflow as when running on 8 cil. This mechanism HALFS the pump losses.
Combining this technology, would povide a mechanism to reduce the pump losses with a factor 8, but only at very mild regimes. When you would demand more then 25% of the output (torque that is, not power), the cilinder switch out should stop and only valvetronic remains active. I guess this is only usefull on very long high road trips with moderate speed on a flat high road that is.