In many places, there are no safety deposit boxes (vaults) available to regular people anymore. In my country, there are zero options and the only recommendation is to put your valuables in a safe in your home (which has a completely different security model than a bank vault).
How do you put bitcoin in a bank vault?
He’s saying put regular money in the bank vault, why complicate with crypto.
You create your seedphrase - the famous 12/24 words, print them on a piece of paper and put it in the bank vault. Ideally some sort of fireproof container/envelope around it, and if you plan on long-term storage rather write them down manually with long lasting ink pen.
You buy a little bit of titanium sheet and some alphanumeric punches and you punch your seed phrase into it. It won't matter if the bank burns down or gets flooded, your plates will be fine.
Most people probably don't have the know how or equipment to punch titanium which adds a possible supply chain/side channel attack too.