I am working on Extensor Action. I'll tell you what I'm feeling and seeing as I work with it. I Hit and use a Sweep Release. What I'm seeing on video is a later release. So in a way, there is more effective club lag.
I feel greater and more consistant pressure on PP#3. The distance and lower ball flight seem to confirm the better clubhead pressure lag. My video camera is analog, so the higher speed Actions are hard to pick up. But it looks like I'm holding the Wedges and clubhead pressure lag slightly further through the ball. I was losing some of my right Wedge on the Downstroke. I think the constant Extensor Action does put a Checkrein on the package that helps me hold on.