Currently, there’s a difference in clicking on suggestions on Special:Search and in default search bar.
- Special:Search ones redirect you to another Special:Search page before you can go to the article,
- and the search bar redirects you to the article itself.
I have no doubt that this difference in UX is confusing for the most people who try to use autocomplete, so I suggest to bring it to one default behaviour (redirecting to articles, since there’s no way that autocomplete can contain non-existing articles). I’d think that this non-standard behaviour was brought somewhere from OOUI, but you never know.