Central banks do not have a great track record in their gold trades. The Bank of England, the UK’s central bank, sold the bulk of its reserves for $250-270 in 1999-2001, just before the gold price took off.
CB’s are not traders.
Traders would use the paper gold/silver market via futures or etf’s.
No, this is a hedge against an increasingly dangerous and unstable world. You may have noticed the unimaginable and unsustainable debt levels in the USA and other major countries around the world.