He is right, people dont seem to understand the degree of which reflexivity plays in world reserve currencies. When a currency becames as important and widely used as the USD that creates a even bigger reason to use the currency: everyone does so you are forced to use as well, call it the windows effect
This translates into the tendency for the country with the reserve currency to run trade/current account deficits(and a tendency for a secular decline in its value), not because their consumers are spending out of control but simply because that country have the means to finance their high spending through foreign capital flows: the dollar holders have to invest their dollar reserves somewhere, that usually is US T-bonds, corporate bonds(which include mortgage bonds) and stocks, although a significant fraction of US paper currency is held abroad
The dollar is likely to remain the world's reserve currency for longer than anyone expects simply because it makes sense for it to be. When people name XYZ as substitute they seem to forget one thing about them: nobody uses them so why should you, you will end up paying exchange fees and run into conversion issues if you try to do business in a international scale. The world reserve currency will change only when the consequences of the policies of that country get so bad people are forced to change, then reflexivity will work in reverse
