On main Q&A sites, it's always been the case that questions with historical locks are "hidden" or "unlisted" from most users: they don't turn up in any question lists, and only show if someone follows direct links to them.
Since May 2012, though, such questions weren't supposed to be hidden in this manner on meta sites.
But this doesn't seem to be the case anymore. This question on this site has a historical lock, and is tagged community-ads. However, if you follow the tag link above, you won't see that question listed in the list of questions with that tag.
At first, I thought that this was a Meta.SE specific bug, as it was being treated as a main site for these purposes. However, I have two reasons to doubt that: first, this site is correctly classed as a meta site for many other purposes (e.g. allowing unanswered duplicate targets, disabling the
RemoveAbandonedQuestions Roomba criterion, etc.), and second, I found this post which talks about a historically-locked question on a per-site meta that was hidden in the same manner. That post was made in January 2016, so it seems to have been broken for a long while.
Why are historically-locked questions hidden on meta sites now? Is this a (long-standing) bug, or was there a feature change at some point? (Or was the May 2012 edit incorrect?)