I don't know if you have leaf springs or coil, but any place of attachment could be a potential creak point. I believe there may be a sway bar type gizmo on the rear of some vehicles, same thing. If you really have questions about the shocks, you can disconnect the bottom bolt possible and get it out of the way and see if it make the noise anyway, to eliminate it. Did he lube the top and bottom attaching bolts?