You're taking the quote out of context. "High powered money" is not what consumers touch, and it is not the majority of money. In the very next paragraph he says: "Now, you would think that that's a bad idea because there would be no provision for expansion; however, high-powered money [currency plus bank reserves] is a small fraction of total money and the ratio of total money to high-powered money has been going up over time."
For the definition of "high powered money", see: https://en.wikipedia.org/wiki/Monetary_base ("in economics, the monetary base (also base money, money base, high-powered money, reserve money, or, in the UK, narrow money) is defined as the sum of currency circulating in the public and commercial banks' reserves with the central bank.
The monetary base must not be confused with the money supply which consists of currency circulating in the public and non-bank deposits with commercial banks. Normally, the money supply excceds the monetary base by far; the ratio of the two is referred to as the money multiplier. If one excludes currency from the definitions, the monetary base is not a subset of the money supply - rather, the two are disjoint sets. On the commercial banks' balance sheets, the former belongs to the assets whereas the latter belongs to the liabilities.")
With Bitcoin, the total money supply is fixed (which Friedman acknowledges as a "bad idea" in your quote), not just the monetary base, because there is no fractional reserve banking in Bitcoins (or at least I'm not clear how you'd build fractional reserve banking on top of Bitcoins).