The truth is not up for a vote. There is only one truth whether a majority believe it or not. If a poll could decide these questions, we might as well drop this discussion now because a majority of people believe JFK died as a result of a conspiracy and that would make us both wrong. I don't know what you are looking at. There is no question JBC's head is turned far more than his shoulders [in Z-193]. His head/shoulder relation looks very similar to what we see in JFK whose head is turned sharply to his right while his shoulders are turned slightly left of Zapruder's sight line. We can see the left side of JBC's face, and we'd even be able to see his ear if the overhead bar were not blocking the view. If his shoulders were turned that far, we'd be able to see the outside of his left arm. Instead, we have a frontal view of his chest.
Question: Why has Rosemary Willis stopped looking at JFK and Jackie in Z-193 and turned her head towards the TSBD?
Answer: Because she heard Oswald's first, missing-everything, shot -- as did JBC, who, having already turned his head quickly to his left starting in Z-150, has turned it far back to his right in an attempt to catch a glimpse of JFK over his right shoulder.
It's interesting that Jackie has turned her head far to her right in Z-193, too.