You gave me your interpretation of why Jackie's testimony doesn't tally with the Zapruder film and that's all it is - an interpretation since you are not an expert in this field. The real reason for the two not tallying and for JBC's testimony not tallying with the Zapruder film as far as I'm concerned remains unknown.
You said: "You're not an expert in this field."
What "field" are you referring to, Slater?
Anyone with an open mind will discern that Jackie is looking to her left in, for example, Z-161, that she's looking straight ahead or a little to her right in Z-180, and that she's looking to her far-right in Z-190.
The reason Jackie's testimony didn't "tally" with what we see her doing in the Zapruder film right before her husband was struck in the lower neck/upper back by CE-399 is due to her very human "failure" to remember that, although she'd been looking to her left for a long time, she had turned to her right around Z-175 to look at, and probably smile and wave to, Mary Woodward and her three journalism colleagues.