IMHO everything true is moving towards precision. you are correct about the ground lug due to the factory ones needing as much as .020" to get cleaned up on the Blanchard. As for the NSS nut, how do we know the factory ones are not just as true? Try putting some 600 grit on a clean flat surface and using light pressure rub some small figure 8's with the face of your nut.

You will realize the accuracy potential when you have the face of the action trued. For ultimate precision you need to have the threads trued to the centerline of the action and the barrel indexed with the bend of the bore to the vertical axis of the action. It would not hurt to have the mount holes redrilled with the centerline as well. You would probably go with a custom if you needed that kind of tool though.