No. You see, the thing about phpBB permissions is that any person can have any single permission. That means that a normal user could, if the Administrators so pleased, have access to create forums but no other higher permissions, or have all of them, or only be an Administrator but not a moderator, or any other insane combination of permissions. A user must not be an SMOD to be a group leader, all they need is the correct "permission mask".