If you think of it as a keyring there's nothing wrong with not backing up the keys by default. You are right, however, that it should inform the user about the

If you think of it as a keyring there's nothing wrong with not backing up the keys by default. You are right, however, that it should inform the user about the importance of having more copies of the keys if the service doesn't implement backup codes. Personally I prefer to transfer key clones directly to backup devices without the need for the backup device to be online. The few keys that I lost due to MS Authenticator were from a time before I introduced this process.