authconfig has an entry for configuring LDAP both on the first and the second screen. Unless I missed something I suppose one of them can be removed.
The two screens serve different purposes. The first screen's toggle controls whether or not LDAP is consulted for user information (i.e., home directories, shells, etc.) and the second controls whether or not it is used for authentication. On my test machine I use LDAP for user information and Kerberos for authentication. All the same, allowing the user to set the server options doesn't quite make sense on both screens, so that'll change in 4.0.27 and later.