You can already say that if you use the monetary base (M0) instead of M1. These 11M bitcoins we are using in this calculation are Bitcoin's monetary base and M1/2/3/4 as Bitcoin has no fiduciary money so far.
Yeah, I agree. The bitcoin float is more like M0.
Also it turns out these digital fiat bank deposits (M1) are not as sterile as economists/banker/govts would have us believe, it seems like there are hidden claims on them by sovereign and other unspecified creditors (particularly look at deposit "covered bonds" and convertible notes that are being traded against customers deposits in the shadow banking system.)
When you have bitcoin keys in your possession they are clearly more liquid than fiat bank deposits, so it is more like cash and coins i.e. physical currency. Imho the globe is slowly waking up to the fact that digital fiat is actually encumbered with liabilities and not as good as money as physical cash.