I was talking definitions.

If a market prices an asset using a common unit, then that unit represents the "base monetary unit" for pricing purposes. If you care to check across all cryptocurrency exchanges, you'll find that 99% of all cryptocurrencies are priced in Bitcoin.

That in itself makes Bitcoin the "base monetary unit" of the entire cryptocurrency economy, however there is another, more fundamental basis for that terminology - namely the fact that Bitcoin is an unbacked monetary token, just as gold was.

Any economy needs something which can function as a monetary medium. It's very rare to find a candidate that works as such because the requirements of a monetary medium are so demanding. Gold worked in physical markets because it's one of the few elements that isn't found in abundance.

Until 2009 there wasn't a single technology that could fulfil that role on an electronic platform - you needed counterparties (otherwise known as 'banks').

So saying that "Bitcoin is a protocol" is a bit like saying "Gold is a metal" - i.e. true but not very relevant to its potential monetary function.