I guess what I meant by efficient was, the theoretical calculation which doesn't account for energy loss comes close to the actual observed value. Not efficient as in harvesting energy from fuel
That isn't efficiency, that is science (properly) meeting with reality
If your fuel trims are near zero, the theoretical value for injector time matches the actual requirement. Nothing miraculous about that; that is the purpose of having an ECU in the first place
It has nothing to do with energy loss. A certain amount of air measured requires a certain amount of fuel mass for stoich.
The engine could be 1% efficient or 100% efficient, that amount is the same.