Sorry, but I think you are missing the point (please see my follow-up post). The point is, search results are not static even for the same inputs (search string, location, etc), even in privacy mode.
That's great that you use DDG and find it useful! If Google was a true monopoly, as the current media blitz would have you believe, then you would not have been able to so easily switch to DDG (or Bing, or...).