This is incorrect. Fallback-Mixing, if you have enabled it (which requires Brave), issues an anonymous query to Google, lacking any cookies or other persistent state for that domain. These results are then presented along with Brave Search's own results. There's no tracking involved. If you perform a direct Google search, you're passing along your cookies as well.

The user was replying to using DDG with !g

In an indirect way, it’s possible by doing !sp on DDG, which redirects the search to startpage, which shows untracked google results.

Ah, my apologies for any confusion. For what it's worth, the !sp bang is supported on Brave Search as well :)