I thought that was just a visual indication of the direction of the camera relative to the plane?
Might be useful to track that in After Effects. It's finer grained than the ° numbers, and could tell us something about the ground tracking mode which confuses people.
That's how it seems to be behaving in this video, which would be redundant. In the Gimbal video, the dot is almost at the top when the azimuth reads zero, but it reaches the top when the azimuth is about 6 degrees.
Edit: On second thought, I guess it's at the top at 0 degrees. It's hard to read because it overlaps other symbology. So camera direction makes more sense.