That explains it, because openSUSE uses snapshots and quotas by default. It creates a snapshot before and one after every package manager interaction and cleans up old snapshots once per day.
Unfortunately, deleting snapshots with quotas is an expensive operation that needs to rescan some structures to keep the quota information consistent and that is what you're seeing.
I'm not sure that's correct. When you install openSUSE (this was a clean install) there's a checkbox that asks if you want snapshots, which I did not enable. But either way, a fresh openSUSE install with XFCE on Btrfs rendering the computer unusable for, at least, 2 days is not okay in my book, even if snapshots were enabled.
Unfortunately, deleting snapshots with quotas is an expensive operation that needs to rescan some structures to keep the quota information consistent and that is what you're seeing.