A system restart shouldn't be necessary to get that fix to work. All you are doing is putting a "signpost" to PTW Game Data in the place where the mod is looking for it, and calling it CIV3PTW. So as far as the system is concerned it's no different from copying that directory into the mod, lock stock and barrel, except you haven't used any significant disk space. By the way, once you have made the symlink called CIV3PTW for the first mod, you should be able to just copy it into another mod folder to achieve the same effect for that one. You don't need to go through all the Terminal steps again each time.