Brave Search redirects to websites via Google

seize:

Importantly, from my limited testing “google fallback mixing” is not a toggle-able setting for brave search outside of brave browser

Right, I think that’s because this is a Brave browser setting. As the linked page states:

…you can allow the Brave browser to anonymously check Google for the same query

So it’s the browser making the request, not the Brave Search server. The query results are then shared with Brave Search to help improve the index.