[Yoda]

If you trace the Arc of approach, wouldn't that bend the plane line?

It depends on what is doing the tracing (of the Arc of Approach).



If you use your Right Forearm to trace, there is no bending of the Geometric Plane Line (the Baseline of the Inclined Plane). Remember, the Right Forearm simply is not long enough to cover the Arc of Approach; hence, it can only trace it. As the Right Forearm traces the Arc of Approach, the Clubhead covers it (and the Clubshaft remains On Plane and pointing at the Plane Line).

However, if you use the Clubhead to trace, then you are correct. In this instance, the Plane Line will indeed be bent. In fact, it will be bent anew every split second of the stroke.