The behaviour is most obvious when your avatar's position is only just off the World Map window. The longer the distance between the circle arc and your position, the less obvious the offset is. It seems to vary with the position of the circle in relation to the edge of the map window. In the first of these screenshots, you can see that the circle is not centred on my avatar's position:
If I push the map up a little, the arc "jumps" suddenly to a new orientation that *is* centred on my position: