Misleading.
People for years have tried to claim the BIS is "sovereign" as in it is above law and it's own country. Simple research shows otherwise, but the easy catch-all response will be given: It's so secret and powerful you can't learn the facts.
For the US the BIS falls under 22 U.S. Code § 288, International Organizations Immunities Act. A far stretch from a sovereign country with no adherence to law. It's primary "above the law" asset is its immunity from legal proceedings, including assets.
https://www.bis.org/about/hub_order.pdf It's legally sovereign, but not a country. I don't know why everyone thinks anything "sovereign" is a country.
Back when PG was claiming US banks should hold cash for every dollar on that bank's accounts I got in touch with BIS to get exact accounts of what the best volumetric algorithms were. PG like many forget that US banks hold money other than US dollars, so all of that has to be taken into account as well.
The amount of warehousing even a small bank would need is significant. I imagine bank fees would skyrocket if they had to keep all that cash on-hand.