Not an «apple fanboy». You should justify that TDP is the measure we are looking for, instead of just the available measure. TDP is a
maximum, and an average one for that matter.
Those measures should use something like `powerstat` results standardizing other conditions - in fact, they should use benchmarking (just like the numerator of the numbers you report does, but not the denominator). This system here has a TDP of 6W, but uses 3.3W during light use, and peaks around 7.5W.
Sure, there could be a literal interpretation of "Performance/Power" which somehow could link speed and TDP (benchmarking at the same stated TDP), but (°) it would be imprecise as TDP is an estimate (so consumption should be benchmarked) and (°) it would not represent some more useful scenarios like "which system allows squeezing more working time out of a battery" (which is not represented by considering maximums - especially given technologies like big.LITTLE).