It would be nice to have the option to click on the parent group on a catalog and have all the children items be displayed in the filtered list in addition to children group links. This could be accomplished by optionally adding ',' . $twig->tid to parent paths for each child.
I have added a patch to my version of the code and love the results. Making it optional would require an admin option on the view. I made change effective on all catalog displays by adding this line to the uc_catalog.module after line 514 in version 7.x-3.4 of ubercart.
$branch_path = $branch_path . ',' . $twig->tid; // StudioFX101
To see a sample visit studiofx101.com and click on the catalog.