Proffering something such as this to prove the SBT only makes plain how absurd this 61+ year old THEORY is.
I have to agree with you that David's suggestion that JFK is not reacting until z226 is difficult to accept. The difference between z193 and z225 (less than 2 seconds) is striking:

In z193 he is smiling and waving but by z225 he looks like he is posing for an Edvard Munch portrait.