I went from Munich to Italy regularly from 2015-2019, haven't been controlled once at any of the borders.

Have seen French border police (sometimes) at the German-French border down here near Freiburg but not the German police.

But yes, German police was present in Basel some weeks ago when I crossed there. Although they had two cars they controlled and let everyone else pass in the long line that had formed, no matter the car plates.

So not sure if there's really that much to it.