Last go round on this one.
IMO, no one listening to the eyewitness 911 call would have reason to doubt his sincerity or concern or that he saw what he saw. He was very specific, including about the sequence.
But LEO Eric didn't listen to the call. A dispatcher obviously told him about it, because he mentions in his report that someone had reported a male striking a woman. Soon or right after that LEO Eric sees the van driving erratically. That's when the video begins.
On the scene, he sees a clearly upset Gabby who doesn't calm down, and an at ease BL. Both tell Eric consistent stories about her hitting him. He had marks on him. Yes, she has a mark on her face. What Eric the LEO also hears is eyewitness Chris saying that she had fought her way into the van. That's physical. Perhaps the scenario LEO Eric imagined is a frantic Gabby whacking at BL as she enters through the van window, and in the turmoil of that, BL grabbing at her face?
It would be helpful to have heard more in the video of what Gabby said & was told by LE & the woman park ranger.