Bank of England on money creation

The Bank of England have published an interesting note on money creation. Given that Kaleidic publishes our own measure of the UK money supply, there is plenty that could be written about it. For now though, I just want to nip some of the crowing being done by MMTers. The way I understand the "money multiplier" is that there's a ratio between narrow and broad money. It's a bit like saying that there's a link between changes in human generated CO2 emissions and in average global temperatures. But identification of a ratio says nothing about causality. In the case of global warming, it seems that there is a large and vocal group claiming that the ratio (or correlation) is stable, predictable, and underpinned causaility. There's others who dispute this. There's probably even some who argue the causation runs the other way.

In the BoE report they say:

Another common misconception is that the central bank determines the quantity of loans and deposits in the economy by controlling the quantity of central bank money — the so-called ‘money multiplier’ approach. 
central banks implement monetary policy by choosing a quantity of reserves. And, because there is assumed to be a constant ratio of broad money to base money, these reserves are then ‘multiplied up’ to a much greater change in bank loans and deposits
And then the killer argument:
While the money multiplier theory can be a useful way of introducing money and banking in economic textbooks, it is not an accurate description of how money is created in reality. Rather than controlling the quantity of reserves, central banks today typically implement monetary policy by setting the price of reserves — that is, interest rates
Obviously this depends on the textbook. In mine, I explain how central banks can affect the supply of money (through open market operations) or the demand for money (through interest rates) and the links between the two. I also mention that there is a ratio between broad money and narrow money. But I don't claim that the ratio is "constant". The term "multiplier" implies some sort of mechanistic causality. I think that's a strawman. I believe that considering the ratio between narrow and broad money, and the factors that cause that ratio to change, to be important. 
I suspect that the reason the "money multiplier" is used so much is because it's descriptive and intuitive. The MMT crowd have a grain of truth in their critique. The challenge is to present an alternative that is more accurate but also just as usable. Whenever people criticise "textbook" economics, I wonder if they've actually read any. Or at least if they recognise that textbooks are starting points, and *not* the codification of everything we know and claim to be true.