I wouldn't trust them either, but your claims (that gold is not a currency) are in fact unfounded and don't meet well with reality. There are gold coins minted in many countries, so gold is a currency, whether you like it or not...
Thats the one of the worst arguments I heard: "Gold is a currency just because gold is used to melt it into round circle objects!"
Well then lumber is also a currency because its used to create disk shaped objects from it! Lumber also stores value in the long term! But you will need to carry it on your back to the supermarket
You forget that disk shaped objects from lumber are not considered a legal tender anywhere in the world (afaik), therefore they cannot be (officially) used as money, unless they are declared as such and you are able to pay taxes with them. Besides that, central banks do not hoard timber, they hoard gold. If you are curious, very different objects served as money in various societies throughout the history of humanity. So your analogy is flawed at best, and you can't get away from the fact (or ridicule it somehow)...
Money is an abstract idea, thereby any object (kind of) can potentially serve as it (provided they can perform its functions well enough)