I don't believe the V4 update is needed for S4. However, some recent character sets (which use ExP) have included the batch file and utility needed to perform the updating, so if one of those has been installed and then unisntalled using the uninstaller then those files may be missing and installing any version of V4 (update or the older one) will restore them. But if that is the issue some people are having I would expect an error message from the installer or the desktop shortcut to the updater.

As an aside, you can use S4 either through the Stephanie 4 cr2 (in which case the figure loads with the base morph applied) or through the V4 cr2 (in which case the channels are there but the morphs are zeroed).