His head is turn that far to the right. His torso is not and that is what matters. There is no way a bullet exiting JFK's throat at Z193 is going to go to the left of JBC's torso. It is impossible.
I would be interested in knowing why you think you can determine that without working it out or using an accurate model. We can see that JBC’s shoulders are turned well past the perpendicular to Zapruder because we see the left side of his collar.