The critial alignment is the left arm flying wedge.
What I think you mean, the left wrist being 'flat' visually at release is not actually flat, but slightly arched.
There is no need for 'bend' at release if the proper definition of 'flat' is understood. bent = left arm flying wedge out of alignment flat = left arm flying wedge in alignment.
Take your left hand and grab a bottle/glass or water and lift it up to drink. That is a flat left wrist.
Ed,
He's talking about a Double Left Wrist Bend and how to perform a Non-Automatic Release of #3.
I agree about the Left Arm Wedge. To me, Flat is Flat. Visually, lay a Level on it Flat. Flat Left Wrist, Bent and Level Right Wrist, Uncock and Roll the Power Package on Plane. Flat.