Feature summary: When viewing a category that belongs to a test wiki (i.e. one with a prefix), the pages in it that belong to that same test wiki (which should be all of the pages) should not have the prefix in the category listing.
Use case(s): It is unnecessary and redundant to show the test wiki prefix in front of every page when every single page in the category has the same prefix. Especially for RTL languages, this gets really cluttered, as illustrated here:
Benefits: For the ease of contributors and readers.