Custom Data Group for Relationship - sub types of a relationship should appear on a single line in selector

When creating a Custom Data Group for a relationship, sub types A-B and B-A (ie parent of, child of) of a relationship should appear on the same line in the selector (ie parent of / child of). Currently they appear on separate lines however selecting either one (ie parent of OR child of) applies the custom data group to both relationship sub types.

See http://forum.civicrm.org/index.php/topic,14189.msg60540.html for more info.