Our country and the world are in an entirely different situation/position than it's ever been in history, so prior history doesn't apply to what our reality is today. As far as the Federal Reserve Bank web page, you're getting information from an entity that's desperately trying to hold onto their power. The Federal Reserve is not part of our Gov't. It's owned and controlled by the central bank. They don't want us moving away from their fiat dollars, because that's where they make their trillions & trillions of $. They're not going to come right out and say "yeah, we'll be losing total control of the money supply because the U.S. is going back to the Gold/Silver standard". They're going to be the loser when we make the conversion, so don't expect them to be truthful, expect them to spew propaganda as they do everything they can think of to try to hold onto power.
You're making an assumption that the gold that's currently being produced by the U.S. or that can be bought from other countries, is the only gold that we have, and nothing is further from the truth. The truth will come out to the masses in time, but the U.S. has acquired enormous amounts of gold since Trump's first administration, and when I say enormous, I mean more than enough to totally wipe out our country's entire debt. Stay tuned...