> I actually hadn't realized that each section of the library docs had a "sub-index" page like that
That’s multiple-entry navigation :)  You can jump to a module page, or use the index, or use the search, or browse and see the sub-indexes.

As the docs for zlib, gzip, bz2, lzma, zipfile and tarfile are in the archiving subsection, there’s already a link to the subsection index, so I just removed the “See also zlib, etc.” lines (except for the link from zlib to gzip).  I added a link from archiving.rst to shutil and more links and reST targets in shutil.