Any situation that causes both Password and PrivateKey authentication to be attempted (server requires both, password tried first but is wrong, private keys) will throw CreateMessageTypeAlreadyEnabledForOtherMessageException for message number 60.
The ssh auth spec indicates that SSH_MSG_USERAUTH_PK_OK and SSH_MSG_USERAUTH_PASSWD_CHANGEREQ are method specific, so it is ok that they share message number 60. But SshMessageFactory treats message numbers globally.