I double-checked.  when poser saves a prop in a pz3 file or to a prop library, the reloaded file or prop retains the altered prop origin.  however, when exporting the prop as wavefront obj, then importing it, origin is reset to default, in the case of the poser hi-res ball.  the wavefront obj export format produces a text file describing the surface (e.g. vertex 3d co-ordinates, UVmap co-ordinates, order) but contains no info on origin, as it's not a solid.  hence the easy way to save these is as pz3 or pp2 file.  I can't say it's a bug, as they're limited by the wavefront format.  maybe one of the other non-poser formats saves origin on export.