I have no problem with that drawing. I'll take it at face value. I disagree with your assessment of JBC's shoulder turn. If you are talking about the relationship of JBC's shoulders to the Zapruder sight line, I would say at most they are perpendicular. If anything, they look slightly less. His head is turned much more sharply to his right but certainly not his shoulders. Check the Z193 frame I added to my earlier post. I see more of JBC's jacket on his right side than on his left. That indicates to me his shoulder turn is short of perpendicular to the sight line. If he was turned beyond perpendicular, we would see more of his left side.
Maybe we should have a poll taken to determine what others think on two points:
In z193:

A. Is JBC's face turned relative to his chest or is it facing the same direction as his chest?
B. Is JBC's chest turned to JBC's right of the sightline from Zapruder, to the left of that sightline, or is his chest facing directly at Zapruder ?
I suggest that his face and chest are facing about the same direction or possibly a bit farther to JBC's right a few degrees. I suggest that his chest, therefore, is facing well to JBC's right because we can see the entire left side of JBC's face and none of his right side.