You are confused. There is no separate upstream release called system-utils. OP's suggestion was to package a bunch of the independent tools under a distribution package by that name. systemd-tmpfiles for instance is only called by that name since it was written as part of the systemd project. It doesn't depend on systemd being the init system. Even if reimplementation is needed by distributions who haven't used systemd, documentation on the interfaces already exist and independent reimplementations have been written by various distributions as well.