Just installed flatpak to quickly try out an app and after purging I had over 2GiB left in /var/lib/flatpak.
Anything which is system-installed and can be reinstalled should be purged when a package is purged. Only user-generated content should be kept (although there's an argument that the user should be prompted to remove any personal settings files as well). -- - Micha "The Glass is neither half-empty nor half-full; it is twice as big as it needs to be!"
