Why is the CVT the least efficient transmission yet still fuel efficient?

Hello, CVT transmission from the engine power components is the torque converter, the traditional hydraulic AT transmission is also rely on the torque converter, CVT power transmission efficiency is low as the problem of the liquid AT transmission, as the CVT has countless ratios, the CVT is often to let the engine in the most economical state, and then there is no shift gap interruption of the power transmission, so the inefficiency can also create low fuel consumption. But CVT is not necessarily more fuel efficient than a manual or even a dual clutch.