Hi, I've looked into #585 , which you said is an annoying bug. I have no complete understanding of how to solve it, unfortunately, so I cannot create a PR or post a solution to the issue, but I hope that giving you this partial analysis of the issue here, may help you to solve it:
I noticed that https://www.boost.org/doc/generate.php?page=libs/libraries.htm&version=1.73 shows geometry extensions and https://www.boost.org/doc/generate.php?page=libs/libraries.htm&version=develop does not. After running generate.php locally, I think that it is based on a db of libraries that is generated by update-doc-list.php and represented in this xml file: https://www.boost.org/doc/libraries.xml. It has multiple entries for "geometry/extensions", the entry for develop has hidden status, the entry for "1.70" does not. Notably, "geometry index" has an entry for 1.70 without status hidden and one for 1.72 with status hidden.
What I think, may happen here, is that the generate.php-script just uses the latest numbered entry if version=1.73 is passed. Manipulating the data structure like this in generate.php
$libs->db['geometry/extensions']['1.73.0'] = $libs->db['geometry/extensions']['1.70.0'];
$libs->db['geometry/extensions']['1.73.0']->details['status'] = 'hidden';
makes the "geometry extensions" entry go away, if I run it locally.
So, if the metadata would be added again for the next version with the status being properly set to "hidden", I believe that could make the "geometry extension"-entry go away.
So TL;DR: I think the list of libraries for releases may use the latest meta data for a numbered version and because of that having a non-hidden "geometry extensions"-entry for 1.70 and no entry (deleted) afterwards may cause the entry to reappear in all versions since then.