The final pass is flaked from a straight, heavily abraded, continuous platform that is exactly at the centerline of the workpiece.
The flakes are spaced apart at a regular interval as you flake down the edge... let's say 1/4". Then the workpiece is flipped over and the flakes are removed using the remaining bits of platform that exist between the previously removed flakes on the other side. Again, at 1/4" intervals. You are always removing flakes from the exact centerline... not above or below the centerline.
On the real points I've seen, retouching to remove the remaining bits of platform is not always done.
The more skillful you become at this technique, the sharper your edges will be after the final pass. At first, you will have bits of of the continuous platform remaining. As you get better, you will be able to remove more and more of this platform and you won't have to go back and retouch the edge.
If you look at the cast of the Eden point, you can see remaining bits of the continuous platform.