As far as I can tell, the only way to restore a backup is during the onboarding process. How do partial backups fit into this? If I have a partial backup of HA Core or just an add-on, I still have to reset my whole installation to restore it, which means I must manually re-configure everything else - defeating the point of having backups!
Because of this, the only kind of backup that makes sense is a full backup, as it’s the only one that allows you to restore your system to a previous state.