Sorry, those were poorly chosen examples. Here are some better ones:
I don't think that any of these are hidden, at least by looking for them in
page_props. These are all from the enwiki-20121201 dump.
From: Petr Onderka [mailto:firstname.lastname@example.org]
Sent: Wednesday, February 13, 2013 9:34 AM
To: Robert Crowe
Subject: Re: [Xmldatadumps-l] Housekeeping categories?
Both of the categories you mentioned *are* hidden, so I think you can use that.
On Wed, Feb 13, 2013 at 6:24 PM, Robert Crowe <robert(a)ourwebhome.com> wrote:
Is there any way to distinguish between categories
like History, or
Literature for example, and what I would think of as categories that
are used for internal housekeeping like "Unprintworthy_redirects" or
"Nonindexed_pages"? They're not hidden categories, but conceptually
there is a clear difference between housekeeping categories and
categories that define fields of knowledge. But is there anything in
the tables that distinguishes them?