On the grand scheme of things this is 12bil usd worth of gold. The GDP of Netherlands is 1.4 trillion USD. So, this is honestly a foot note.
To put in human terms, it's roughly three day's labor of every worker in the Netherlands.
GDP is just a number in a spreadsheet. This is a physical asset.
Not the right comparison to make when comparing gold vs paper currency that can be printed at a whim. The comparison would hold if they pulled out physical fiat currency reserves.