Forget money and banking for a minute. Let's think about international macroeconomics.
Just suppose the US Fed, for reasons unknown, pegged the exchange rate of the US dollar to the Canadian dollar. The Fed makes a promise to ensure the US dollar will always be directly or indirectly convertible into Canadian dollars at par. The Bank of Canada makes no commitment the other way. The Bank of Canada does whatever it wants to do. The Fed has to do whatever it needs to do to keep the exchange rate fixed.
For example, just suppose, for reasons unknown, the Bank of Canada decided to double the Canadian price level, then go back to targeting 2% inflation. If it wanted to keep the exchange rate fixed at par, the Fed would need to follow along, and double the US price level too, otherwise the US dollar would appreciate against the Canadian dollar. The Fed's promise to fix the exchange rate makes the Bank of Canada the alpha bank and the Fed the beta bank. Both Canadian and US monetary policy would be decided in Ottawa. It's asymmetric redeemability that gives the Bank of Canada its power over the Fed.
Doubling the Canadian price level would mean approximately doubling the supplies of all Canadian monies, including the money issued by the Bank of Canada. Doubling the US price level would mean approximately doubling the supplies of all US monies, including the money issued by the Fed. Because the demand for money is proportional to the price level.
The money issued by the Bank of Canada (mostly currency, with a very small quantity of reserves) is a very small share of the total Canadian+US money supply. What exactly that share would be would depend on how exactly you define "money". Let's say it's 1% of the total. The total Canadian+US money supply would increase by 100 times the amount of new money issued by the Bank of Canada. The money multiplier would be the reciprocal of the Bank of Canada's share in the total Canadian+US money supply. 1/1%=100.
Maybe the US Fed keeps reserves of Bank of Canada dollars, to help it keep the exchange rate fixed. Or maybe it doesn't. But it doesn't matter.
Do loans create deposits, or do deposits create loans? Yes. Neither. But it doesn't matter.
The only thing that does matter is the Bank of Canada's market share, and whether it stays constant. And which bank is the alpha bank and which bank is the beta bank.
In the real world, the US Fed does not fix the exchange rate of the US dollar to the Bank of Canada dollar. But the Bank of Montreal and TD Bank do fix the exchange rates of their dollars to the Bank of Canada dollar. The Bank of Canada is the alpha bank, and BMO and TD are beta banks.
(C/D + R/D)/(1+C/D) is the Bank of Canada's share in the total Canadian money supply, where C/D is the currency/deposit ratio, and R/D is the reserve/deposit ratio. The reciprocal of the Bank of Canada's share is the simple money multiplier.
C, R, and D are all nominal variables. C/D, and R/D, being the ratios of two nominal variables, are real variables. If money is neutral in the long run, real variables are independent of nominal variables in the long run. If money is not neutral, those real variables will not be independent of nominal variables. Plus, real shocks will affect real variables, even if money is neutral.
The simple money multiplier story is a story about market shares, and about beta banks fixing their exchange rates to the alpha bank. If all banks expand together, their market shares stay the same. But if one bank expands alone, it must persuade the market to be willing to hold an increased share of its money and a reduced share of some other banks' monies, otherwise it will be forced to redeem its money for other banks' monies, or else suffer a depreciation of its exchange rate. Unless that bank is the alpha bank, to which all the beta banks fix their exchange rates. It is the beta banks' responsibility to keep their exchange rates fixed to the alpha bank. The Law of Reflux ensures that an individual beta bank cannot overissue its money beyond the share the market desires to hold. The alpha bank can do whatever it likes, because it makes no promise to keep its exchange rate fixed.
Just another way of looking at things. I think it's simpler this way. And much more general, because the same story works across international boundaries, under fixed exchange rates. The US Fed used to be the alpha bank for most of the world, when all the other banks pegged to banks which pegged to the Fed's dollar.