Counterexample: Storing the bcrypt hash by appending it to a CSV file containing the usernames and hashes of all users then having a login process where that CSV file is downloaded to the client and the password is verified locally against that CSV file using client-side JavaScript would probably be very bad.

Cryptography part is fine but storage or the auth process isn't.

You would like to think that no-one would write their app that way, but there are plenty of slightly less worse things that happen in practice and vibe coding probably introduces all sorts of new silliness.