That's not what that proves lol, but it does prove that the gold standard does not work and is not sustainable.
You should probably read up a little bit on history, the facts disagree with you. The US government had to use regulations and policies to influence the supply of gold: grants for gold mining, setting the reserve rates, hoarding gold to keep out of circulation. Until the gold standard dropped, there was even a limit on the amount of gold one could legally own. On top of this, other gold producing nations had the power to directly influence US monetary value and undermine US sovereignty.
Throw in implications and challenges of being a global reserve currency (Triffin dilemma), and you end up having a really bad time with an unhealthy economy.
Foolish people that don't know history want to pretend that the gold standard magically creates some kind of natural currency free of "government meddling", but the reality is that even more meddling and government control was required under the gold standard than compared to fiat currency.
Ahhh! I understand what you are misunderstanding, now. You think that I said that the change in size of the pool of currency IS the change in the size of the economy itself. Here's what I said:
The pool of currency and the economy are two separate things that can grow at two separate rates. It just creates serious economic problems when they are not aligned with each other. Homework assignment: read up on the Great Depression.