Yes, the other account was not a call. It was a written statement made *after the stop*. We do not know if the statement was prompted with a neutral question, "tell us what happened," or if it was prompted by something more leading, like "did you see GP punch BL? Tell us the story from the beginning." There are reams and reams of papers on how much the question influences eyewitness accounts. A spontaneous contemporaneous report to 911 is by nature more reliable because it is not filtered through memory nor is it prompted by questions.
The questions matter a lot. See, for example, Elizabeth Loftus' famous studies about eyewitness accounts of an accident. If asked how fast the cars were going when they "collided" you get very different answers than if you ask how fast they were going when they "smashed into" one another.
Car Crash Experiment – Exploring Experiments