The subject/chapter/section information is taken from the file taxonomy2 in the OPL folder. Accessing it on GitHub will always have the most up-to-date version.
Regarding the wiki, we are aware that it needs much organizational work. We are currently looking for volunteers to help with this project (and others). When you identify missing information, the best thing to do would be to add it, as anyone with an account can edit the wiki. Barring that, any feature request should be added as an issue on https://github.com/openwebwork. For anything documentation related, you can create an issue in the docs repository. That way if we do have people wanting to work on these requests we'll have a record of what needs to be done.