The Left Wrist remains Flat through Impact, through the end of the Follow-Through (Both Arms Straight / 8-11) through the Flat and Swiveling-Back-On Plane Flat Left Wrist -- I know that is an "extra" Flat but I can't help myself and neither could Homer! -- until the Club flashes around the Hands. [The Right Wrist loses its Bend as the Left Wrist completes its Hinge Action and Swivels back onto the Plane.] Then, and only then, does the Flat Left Wrist Bend -- as the Right Wrist Flattens against the Plane -- and that Left Wrist Bend quickly returns to Flat as the really good players restore their Finish alignments.
And I'm continuing to work on my 'Leakage' move. My first professional lesson was at age 17 with George Preisinger at the old Marietta Country Club in Marietta, Georgia. His daughter, Carol, is now a Golf Magazine Top 50 Instructor at the now-renamed same club. Anyway, he got me to keep that Left Wrist Flat and turn it to the ground through Impact. And believe me -- you are very right -- any leakage' -- and maybe even without any but with an extra good Swivel -- and I was 'Fore Left!'
Along the way, I learned that a Swivel Action was not a Hinge Action, but neither was a Bent Left Wrist an acceptable substitute for a good Finish Swivel. The good news is that I don't hit 'rope hooks' any more, but I'm still trying to get it right. I'm only 58, so I've got a few more years yet!
Meanwhile, I'm resigning myself -- somewhat -- to the Retief Goosen look through Impact, especially when I Swing. I'm not quite as bad, but I still don't like it...