Rear-View vs. Side-View
I agree. I set my mirrors the same way. And it works great for me.
All three mirrors have a different purpose. The mirror in the center of the windshield is the rear-view mirror. The mirrors on the doors are side-view mirrors. Most people (including the author, Nguyen) seem to be confused by both the terminology and purpose of the various mirrors.
As a car comes up behind you it should appear first in your rear-view mirror, then in your side-view mirror, and finally in the side window. As you pass a car, it should appear in your side window, then the side-view mirror, and finally in the rear-view mirror. If your side-view mirrors are properly adjusted there will be little or no overlap between the rear and side mirrors.