I've noticed that assigning the category tree content box to the "View Listing" page, it doesn't display when I view a listing. But if I turn it on as Sticky, then it will show on the "View Listing" page.

Also, note that if I turn it on as sticky or if I turn it on for the "Add Listing" page, then when I visit the Add Listing page it doesn't show the listing category tree, but only shows the word "listings".

I have posted a support request.