[Daryl]

I'm sure someone with more anatomy knowledge can give more detail, but when I interlock the left forearm rotation is checked, it just doesn't want to roll.

I'm guessing it is in part due to activation of the muscles supporting the thumb and forefinger of the left hand (separate your index/middle finger in a 'V' as wide as you can to feel what I'm talking about.

Sorry I can't give you more, but at least for me the difference is clear.

I agree. Especially when Chipping and Pitching.

With an Interlocking Grip, with any tension or lack of Right Arm bend, the Left Wrist doesn't seem to want to fully Uncock which certainly affects the Impact Swivel. Not that you want to be fully Uncocked at Impact, but by disturbing the Uncocking Freedom even the slightest seems to affect the 3 dimensional Impact.

There are days that any of that doesn't seem to be the case, but for general purposes, the Overlap ALLOWS the Left Wrist more freedom of motion.

The Little Finger of the Right Hand seems to grasp tightly when Interlocked. I think it's best not to allow that to occur.