I'm quite confident that governments aren't that powerful.
They can issue money, and manage their currency. But I've never heard about any government actually controlling what currency people use. Not even extremely authoritarian ones.
Can you pay your taxes in another currency?
I think this idea is more about using technology and a digital currency to restrict what can be purchased with a specific digital currency. You said "controlling what currency people use" which I take to mean something different. They are both pretty terrifying and I'm not as optimistic as you.