Unfortunately he is wrong: that is exactly what the prerequisite of real independence is. Without its own currency x would not be truly independent, most especially from the y. Let me just list the things over which it will have no control if it pursues monetary union.
X would not have an effective central bank, which many see as key to economic policy. You can’t have an effective central bank without your own currency.
As a result x would have no control over the amount of money circulating in its economy, and so will not be able to use that control to influence the economy, including its inflation rate, which will be entirely beyond its ability to address.
Nor will x be in control of its own government budget, so it would not be able to stimulate the economy by running a deficit, for instance. That is because the Government would be forced to balance its books unless it borrowed in a foreign currency, which would make it hard, if not impossible, to maintain parity with the pound.
And x would not control the interest rate at which its government and the rest of the economy borrowed money and would instead have those rates (and other conditions) imposed upon it.
In other words, for all practical purposes, the xish Government would have no effective control of any of the measures used to control its economy. In fact, it would be worse off than it is now. It would have, post independence without its own currency, about as much power over the economy of x as a local council has over that in its district, which as any councillor will tell you is minimal. It’s fair to say that such a xish Government would be in office but virtually powerless. It is very hard to understand why anyone wishing for independence would wish for that.
All quite correct. Tuber is talking about Scotland and the pound of course, but it does all apply to the euro as well. In fat, it’s a rather good description of why the euro is such a bad idea, isn’t it?