This analysis is great, and I don't mean to knock it, but one of the things that it doesn't capture is, what choices does the frontend make that impact the amount of work that the backend does. That is, some of the work attributed to the backend could be improved without touching the backend.
That is of course true, but if anything that just proves more what I said. Also that too is part of the "common wisdom" (that as I said, is not always true).