Banks only hold some of their assets as central bank reserves, but solvent banks always have more assets than liabilities.

For a stablecoin to operate like a bank they would have to issue loans (loans are an asset to the bank to match the deposit created when they lend. A regulated bank also needs a certain percentage of owner's capital (paid up shares/retained profits) compared to how much they lend in case of delinquent loans).

A stablecoin just creating tokens with no backing would be fraud, same as if a bank just credited an account from nothing.