I don't think he really said this. The exact quote is

If you want to measure the intelligence of a system, I would suggest measuring its optimization power as before, but then dividing by the resources used. Or you might measure the degree of prior cognitive optimization required to achieve the same result using equal or fewer resources. Intelligence, in other words, is efficient optimization.

This seems like just a list of different measurements trying to convey the idea of efficiency.

When we want something to be efficient, we really just mean that we have other things to use our resources for. The right way to measure this is in terms of the marginal utility of the other uses of resources. Efficiency is therefore important, but trying to calculate efficiency by dividing is oversimplifying.