Go back to the video and you will find that the Flat Left Wrist is not the problem. In fact, the student exhibits a good intellectual and physical command of that alignment.
Instead, the problem is an exaggerated Axis Tilt during the Start Down and Downstroke. He achieves this over-tilting of his spine (back and away from the Ball) by dropping his Right Shoulder severely Under Plane. This misalignment, in turn, is achieved by allowing his Head to drop back and down -- he Sways and he Bobs. The result is obvious: He continually hits 'up' on the Ball -- Scooping -- all the while doing a yeoman's job of maintaining a Flat Left Wrist.
In fact, he apparently has absolutely no sense of the correct Three-Dimensional Impact Geometry (Down, Out and Forward), much less how to achieve it. Thus, the cure is not more work on the Flat Left Wrist, but on teaching him (1) how the Body Pivot works in the correct Start Down; (2) how his Head should be positioned at Address; and (3) how to maintain that Head Position from Address to the end of the Follow-Through (Both Arms Straight position).
In other words, this student has Pivot and Stationary Head problems (Zone #1), not a Flat Left Wrist problem (Zones #2 and #3), and they must be treated accordingly.
Lynn,
You are precisely on point as always. I went back an reviewed. That guy had a very perverted idea of axis tilt. It was even present at address. Then from the top his left shoulder shot straight up in the air. With that pivot he had no chance of achieving any DOWNARD dimension. Even though his left wrist was flat. Zone 2 and Zone 3 can only be as good as Zone 1.
Very nice analysis. It's like EC says, "Just stand there and take it up with the Right Forearm."