[Yoda]

4. The left arm swing plane line, flip release. (pivot-controlled procedure) (The first I'd heard of this left arm swing plane line.)

See 10-6-D / Turning Shoulder Plane / '-B Version' (Vertical Left Arm Swing Plane).

Here:

The arms hang at Address and move in a simple back-and-forth up-and-down straight line path while utilizing the Throw-Out Action of Accumulator #3 [Left Arm and Clubshaft Angle] to 'flip' the Club 'on plane' past the Hands at The Top and 'in-line' with the Hands at Impact.

As always, remember that the selected Plane Angle (and its Base Line) is independent of the employed Release (10 / A-F).