The property in the box was never the bank’s property. They’re just renting a space for you to keep your stuff. In a bankruptcy, that contract could be sold to a third party who takes over the management of the boxes, but the contents are yours.
When you send money to Coinbase, it’s not like that. This latest disclosure makes it clear assets held at Coinbase (or other exchanges) aren’t yours in any sense.
When you get right down to it, as a purely virtual asset the crypto isn't anyone's property. Coinbase holds some keys which give it the ability to sign transactions on the blockchain, a service which has value. They owe their depositors the service of signing such a transaction on request transferring some quantity of deposited crypto to a suitable withdrawal address; the value of this service to the customer is the market value of the crypto. However, it does not seem likely to me that this service Coinbase owes to its depositors would be prioritized over their other debts, especially if that meant selling off other property to buy crypto so they could complete the transfers.
When you send money to Coinbase, it’s not like that. This latest disclosure makes it clear assets held at Coinbase (or other exchanges) aren’t yours in any sense.