He could then add himself to the wheel
He could then add himself to the wheel group if he wanted. This is bad. You could disallow root logins on the console, but you might need them sometime. The existence of the wheel group does not mean that you can skip hiding your root password! If you have no users in the wheel group, then only the root account can get root access (without exploiting some sort of security hole, of course). If you forget to add your first account to the wheel group, you will need to log in to the console as root and make the necessary changes to /etc/group. If you’ve disabled root logins on the console, boot into single-user mode and make the changes. Page 147
Hint: This post is supported by Gama besplatan domen provider