Earlier quoted context omitted.
You are looking at the wrong metric, it seems like they count only transactions, not holdings. Only Fort Knox holds over 4000 of metric tons of gold.
Sorry, I'm not following. The thing that makes a store of value useful is stable demand. This metric demonstrates stable demand. Holdings are irrelevant. As an example of the difference, look at oil or bananas. Demand for those is significant, but because storage is inconvenient, holdings are low compared with total commodity flow.
Transactions are necessary but insufficient for something to become a store of value. For example, steel is sold in great amount, but it is not a store of value.