What this is missing out is the fact that there are now digital currencies of nations as well, for example petro which is still digital currency but at the same time based on a nations resources so it can always be combined.
Bitcoin was never the first digital currency, it was only the first one that seen this much adoption, there was e-money type of deals before that never got too big because they never had blockchain behind it, what made bitcoin original and unique was the blockchain, otherwise digital currency has been as old as internet itself, even data was seen as money at one point and exchanged for fiat currency to be used. Hence there are other smaller details that should be invested some research into before this theory could be 100% done with.
What you missing is the fact to realize difference between crypto currencies and fiat currencies. Digital is just expression, fiat is digital long before bitcoin, people use paying cards for decades. Where is the difference? Of course in what kind of principles currency is using for generation, distribution and transactions. Bitcoin is the first crypto-digital-currency build on blockchain technology.