AH, my apologies. In my experimenting prior to this update, I had enabled a special flag in Brave - and that combined with the update seems to be what allows it to work.
In brave://flags find #enable-autofill-virtual-view-structure and there’ll be a new “Autofill Options” in the General settings that allows you to switch from Brave Autofill to Android Autofill.
Bonus: If you want PassKeys to work, you’ll need to enable #web-authentication-android-credential-management as well.