[Loren]

Can you set up at impact fix with everything on plane? Yes.
There's the answer.
The left arm is not on plane (#3 accum) by definition.
The right forearm is, with a little bend left in the elbow. (Impact is to occur before maximum extension.)
The definition of the Flying Wedges.

If the right shoulder does not move down on plane, it must move somewhere else, which requires compensation.
ndwolfe is not moving the right shoulder down the plane angle. It could be the right hip is in the way.