Both SVG and Motion define equivalent paths for an essentially identical set of shapes. For rectangles and polygons, their definitions are identical, but for circles/ellipses they're not - SVG defines that a circle's equivalent path starts at its rightmost point (cx + rx, cy), while Motion defines that it starts at its topmost point (cx, cy - ry). They at least both agree that the path continues clockwise.

Should we align these definitions? I'm inclined to take SVG's definition just because it has earlier claim, and it seems more likely to break something if we changed SVG.

Edit: I was gonna add a comment about polygons actually being different too wrt initial direction, if you start the polygon with several identical points, but actually SVG2 has some pretty good text defining the direction of a path, and it matches up with what Motion has defined, just in a more generic fashion.