Depending on which reports people were listening to they would most likely believe what they were being told.
Would you report what you were told or would you report what you recalled hearing?
Witnesses are supposed to report what they saw, not what they were told, or “know”. But they commonly don’t do that.
People’s memories are affected by what they are told, or learn. We edit our memories without being aware of that. That is how, even after more than fifty years, I can still remember hitting 400-foot home runs while in little league. Actually, I don’t, but my memory may be off.
Based on my memory, which I think is accurate (but might not be) a motorcycle policeman, following up about 100 yards behind the president, reported in 1976 (?) that he remembered seeing Jackie climbing out onto the trunk of the limousine. However, he made no such claim in 1963. Plus, at the time Jackie was climbing onto the trunk, he was just turning onto Elm Street. So, because of the slope of the street, it would be difficult for him to see the limousine. Plus, there would many vehicles in the way, blocking his view.
So, what is more likely, is that the officer saw the Zapruder film, and incorporated his memory of this film into his memory. He ‘edited’ his memory. And now remembered seeing, in person, in real time, Jackie climbing out onto the trunk of the limousine, while he was riding his motorcycle.