It's not a big win because the OS shouldn't have much data of any value, for similar reasons we don't generally back up our OS installs. It certainly shouldn't

It's not a big win because the OS shouldn't have much data of any value, for similar reasons we don't generally back up our OS installs. It certainly shouldn't be in the same pool as your actual data, the stuff you back up. /home can live in that pool though. I have to squint really hard to see the upside of snapshotting anything other than things like /etc - I have in the past put /etc in git just to track ad-hoc changes. Overall, for the base OS, a minimal set of defaults + a provisioning script does me.