Since 2013 the Help Center search includes privilege pages. The search results seem to be network-wide, with site url placeholders. The shared search index is an issue for the reduced ads privilege, which is only active on a subset of sites since the other sites don't have leader board ads (above posts) which are targeted by the privilege. Therefore, for example on TeX.SE https://tex.stackexchange.com/help/search?q=advertisements returns a search result for https://tex.stackexchange.com/help/privileges/reduced-ads, including a content preview for that search result, but the linked page doesn't exist and redirects to the general privileges page.
This mismatch is very confusing when trying to find information on the privilege for a particular site if you already know something about it from other sites.
The issue is similar to "Secret" Documentation Privileges on sites other than SO but there the privilege, and the page describing it, wasn't only searchable but it actually did exist (while it shouldn't have), even though it wasn't listed on the privilege overview page.
It is also somewhat related to Privilege/FAQ pages should not show ad reduction privilege on SE sites that don't actually show ads which shows that the privilege can exist for sites that don't have ads (Meta.SE in that case).
In any case I think it is a bug and the search results should not show an excerpt and a link for a page/privilege that does not exist for the site that the search is performed on.
