One definition of Extensor Action is-- "extension without tension". This is referring to LEFT ARM tension.
There has been some discussion whether there should even be any RIGHT ARM tension, especially when employing a Pure swinging Machine.
From my observatons there are some types of SWINGS OR STROKES that do have very little Tension in both arms. Both arms are more Rope-like. Goosen and Miller Barber are two that look this way to me.
If you look at Sergio at Address, and at Impact... his left arm is also slightly bent.
The Extensor Action Technique has been proven by many on this forum and elsewhere to be of great value. The Radius of the Left Arm Rope is maintained throughout the stroke. I believe, however, that it must be done in such a way as not to induce a rigid, muscle contracting tension. The player must still be athletic.
A Hitter, may be able to have more of a certain type of Tension, than a Swinger, but even they probably should not STIFFEN UP their muscles.
If the Stroke is efficient... would not centrifugal force cause the rope to straighten somewhat on it's own?
TENSION is the topic here, by the way, not Extensor Action. Just from some of the posts, it seems that there are some considerable differences in the FEEL and/or the way it is employed by various people... usually relating to TENSION.