Blockchain data is public. They can not fib the numbers like they can now. Just how goldbacks and silverbacks had serial numbers that were directly tied to the physical. Tie these two together, and we now have a fully transparent money system anyone can go verify for themselves.

Yes they can fib the numbers of how much is added on the block chain or not added. They can't change it after the fact but if they decide to report more than they have then blockchain won't necessarily fix that.

The only way to stop them from reporting more than they actually have is by allowing everyone to publicly physically audit the gold so it can match up with what's reported in the blockchain.

That creates security issues and is very likely not ever possible.

Which in my mind makes gold and silver not useful unless it is a local trade.

Crypto on the other hand is all held on the blockchain and it is always auditable by everyone at the source. I don't have to worry about someone fudging the numbers because it lives on the blockchain, it's not reported to a block chain.

CBDCs or Central Bank Digital Currencies are controlled by a central authority. The central authority can create/destroy your account at the click of a button, they can stop o allow transactions at will. CBDCs dont use a blockchain and they are not decentralized. That is not crypto.

You don't need the crypto to be physically backed by something if people demand it. It needs to be limited supply, decentralized, scalable to millions/billions, and secure. What you need are reliable audits that you and I can do on our own. Something physical does not allow us to publicly audit it at will because we have to physically be there to truly audit it.