sumerians denoted everything in silver shekels but trade was done will all manner of commodities, including barley grains. your theory of money sounds like it comes from the Adam Smith cult.
Are barley grains a currency? I'm not understanding your argument here. In a practical sense, cryptocurrencies are far too volatile to use as a currency and the "stable" coins are tied to things like the US dollar. Well, I should say allegedly tied because "stable" coins like tether haven't been audited to actually prove it's tied to the underlying.