This is Part 3 (and final) of my series responding to an iNET claim that Modern Monetary Theory (MMT) and mainstream macroeconomics were essentially at one in the way they understand the economy but differ on matters of which policy instrument (fiscal or monetary) to assign to counter stabilisation duties. In Part 1, I demonstrated how the core mainstream macroeconomic concepts bear no correspondence with the core MMT concepts, so it was surprising that someone would try to run an argument that the practical differences were really about policy assignment. In Part 2, we saw how the iNET authors created a stylised version of mainstream macroeconomics that ignored the fundamental building blocks (how they reach their conclusions about the real world), which means that they ignore important differences in the way MMT economists and mainstream macroeconomists interpret a given economic state. I will elaborate on that in this final part. Further, by reducing the body of work now known as MMT to be just ‘functional finance’, the iNET authors also, effectively, abandon any valid comparison between MMT and the mainstream, although they do not acknowledge that sleight of hand.