I've found that, in my vehicles, Torque does not take into account air fuel ratio, and it does not measure DFCO at all. I find it completely unreliable for fuel economy figures.
Great post by Isaac Zachary.
I was pretty surprised when I found idle is generally controlled by ignition timing in modern vehicles, and not by throttle, or an idle valve, or fueling. I'm fairly certain this is in large part because those methods would respond too slowly for transient loads (electrical, A/C, letting out the clutch), but it certainly seems wasteful to give way more air and fuel than is necessary to idle the engine, and then keep RPM in place by retarding ignition timing.