Several of the password drivers related to other board software require access to other columns of the user table (i.e. login_name, user_passwd_salt, etc..), but $row is not passed in when calling check() on the password manager (line 178 of phpbb/auth/provider/db.php). Additionally, $row will not contain the information necessary as it only contains a subset (line 90) of the columns in the user table and will not contain the custom columns required.