Yes you know that it is, I knew this post was probably coming :)
That's why I said "seems" there could be and probably are engines that fall outside these power numbers but this what I've seen with the somewhat limit builds I've looked at that fit what OP talking about. He can investigate it further or others might bring up other examples that confirm and or contradict.
My point was find similar builds with the heads he wants to compare, look at the power curves among other metrics, not just to go by my observations.