mcc on Nostr: Last night a friend claimed this: People who buy and sell gold as investment don't ...

Last night a friend claimed this: People who buy and sell gold as investment don't trade literal gold, rather they buy and sell "gold certificates" which deed ownership of physical gold in some specific location, which makes sense, except he also claims there are several more times gold certificates in circulation than there is actual gold in storage on planet Earth. So some of the certs are fake but we can't know which ones unless everyone sells at once. Can anyone help me confirm or deny this?