Is your skinning affected by whether or not you extrude child zspheres from the top or bottom of a parent zsphere as opposed to extruding new spheres from between the top/bottom of a parent sphere?
The point where a zsphere is added has no effect on how that zsphere adds to the generated mesh. Or rather, there are no special properties assigned depending on where you create zspheres.
The generated mesh is entirely governed by the ultimate position, scale and rotation of the zsphere and it’s relation to other zspheres.