2. thanks for clearing that up. so even in a zero shift swing the right shoulder shifts planes
3. again on which plane?
The zero shift only applies to the clubshaft not shifting, not necessarily other components (like the right forearm, thanks Bagger). Look at 10-13. There are a number of different shoulder turns compatible to the zero shift clubshaft plane. The Standard turn (10-13-A) has the shoulder turning on a flat plane backwards and then on-plane downstroke. That is the one rwh is describing. Probably cause it's in the basic component list for hitting and swinging prescribed by Homer in section 12.
As far as I can tell, you could use an on-plane shoulder turn, but why argue with a man who wrote the book?