JBC specifically described reacting to the first shot also and we see that reaction at Z164, about 5 seconds before Altgens 6.
Take another look at the Z-film. The four motorcycles were even with the front bumper of the Queen Mary. The agents were closer to the motorcycles than JBC was.
JFK wanted to be seen by the crowds. That would not have been possible if the motorcycles were pacing the limo.
It's just stuff you're making up.
Do you even realise that?
JBC does NOT react to a shot at z164. That's just you making stuff up.
The sound of the shot was not drowned out by the bikes. That's just you making stuff up.
Altgens 6 showing Landis, Ready and Hickey reacting to the first shot as they said they did, is not making stuff up.
What if every single person we can see in the follow-up vehicle in Altgens 6 is reacting to the first shot as they said they did, would that change your opinion?