Brian

I hear what youre saying. The key piece in that paragraph for me is the following

Extensor action helps me get to the correct position for the top by keeping me from overswinging and having my left arm move in a straight line along the plane. With too much bend my hands will get to different top of backswing positions dependent on the amount of bend used. Too much bend also means my hands/elbow having to be thrown out at the start of the downswing to straighten my left arm before the forearm can rotate. I also get a late set of the wrists this way which gives me more power with the longer clubs for some reason. On the DS my left forearm can rotate straight from the top, i dont have to straighten it first

BUT I can see how it isnt mandatory and how many people can swing well with bending of the left arm. For me personally im finding it far easier to get on plane with a flat left wrist at the top and then generate more speed and forearm rotation on the way down with the straight left arm

The other key is tension. I feel like my left arm is like a rope at address and I want to make that rope taut at the top but not tense. I want to feel my wrists loose but a slight pulling on my left shoulder blade. When I do this I can hardly hold the position at the top because I have coliled so much and I feel a stretch all down my left side (trying to pull my left heel off the floor) When I bend the arm I release all that pressure and I personally feel theres no 'power' at the top for me to use beacuse I have slack (bend) in the rope as I start the DS. This is why that rope/string drill is so good. Maintaining that radius, that driveshaft

As always I think its each to their own and as always people should experiment with both to see what works best for them but since I have worked on this (since being shown it by a guy I play with) Im seeing better distance and compression with all my clubs