It makes no difference once your into the double points races. I.e. if a guy wins the WDC with 2 races left, he would have still won with normal points, as proportionally the gaps are the same in terms of points available.
Double points in a single race just cuts a race from someones buffer. I.e. if you won with 3 races to go under normal points, that would be 2 races to go under double points for the last race.
Double points in a single race just cuts a race from someones buffer. I.e. if you won with 3 races to go under normal points, that would be 2 races to go under double points for the last race.