Perhaps other officers who arrived later were talking about the event?
The fact the video was edited at all is the issue.
The accusations were that the video was looped late in the footage, the audio was not. Inference being something was cut from the video portion. Irrelevant now because the edits claimed to have been there are not in the video at the link.
AZ, the audio shows that the arresting officer is recounting the incident to a superior on his cell phone. If you watch the whole video, it's clear how the incident escalated, which appears to have been Bland's intention.