The RemoveRegistry table is counterintuitive in that it deletes a registry entry during installation, and not uninstallation. (Unlike, say, the RemoveFile table.)
If you want to delete the branch during uninstallation, you can use the "uninstall entire key" flag in one of the InstallShield registry views; this amounts to installing a key with magic value "-", which causes the key to be wiped out during uninstallation...