There is also no apparent purpose or need for any such person even in a scenario where there were multiple shooters. The motorcade was clearly visible to any sniper in Dealey Plaza. They wouldn't need someone to wave around an umbrella (drawing such attention that we are still discussing it six decades later) at the last moment. That is completely absurd. Anyone who believes this action was somehow related to a conspiracy is beyond reason.
What's the evidence again for these multiple sniper teams?
So the idea - again - is that these powerful groups secretly (somehow; nobody said no?) conspired to shoot JFK in broad daylight in the middle of a crowded street/location with many people carrying cameras and recording the event. And the followup cars in the motorcade had numerous reporters - several with cameras also recording the conspiracy. These reporters and spectators were all over the scene of the crime. Filming things, watching things. Things such as multiple sniper teams roaming about the Plaza (?).
Is this how you pull off the crime of the American century? Really? Like this? Do you want to get caught? Make it as complex as possible?
Vincent Salandria and Jim Garrison argued that this overt plan was done on purpose: it was sending a message to the public that "we" are in charge here and we'll do what we damned want to do. So the absurdity of killing JFK this way - and risking exposure - is really evidence not that it wasn't done but evidence that it was done.
Nuts, just nuts.