> I believe the explanation is much simpler: the glyph simply represents a variety of angles measured from north (the common meaning of azimuth)

The way I see it, it appears to be an arrow curling around the vertical axis, representing the turn from the angle's start to the angle's end. In that sense, the modern curvy arrow actually makes more sense than the original jagged one (which maybe was easier to typeset - or maybe just disproves my theory).