You say its "backed", but what stops them minting more libra than they have "backing" for? Nobody would know any different unless every user attempted to remove

You say its "backed", but what stops them minting more libra than they have "backing" for? Nobody would know any different unless every user attempted to remove all their funds at once. How can you be sure that this wont happen? This is EXACTLY like a bank, but without any of the regulatory protections.