[EdZ]

Correct . . . The release sequence is predicated on the left arm otherwise nothing happens.

So no matter what your procedure the sequence is

1. #4 Left arm moving down the chest
2. #1 The right arm unbending
3. #2 The left wrist uncocking
4. #3 The angle between the left arm and shaft is rolled through the ball

you can view the full release of #4 from a geometric standpoint, or a physics standpoint, ideally both combined.

Geometrically, #4 is fully released effectively at 90 degrees to the ground.

The physics perspective 'can' have #4 pressure through to nearly both arm straight, with the appropriate axis tilt, delivery paths and planes working in the proper sequences and angles. Remember that the right arm is not straight until follow thru, and ideally the right wrist remains bent.

4 barrels are needed to really do that IMO.