By current implementation restore of anonymized backup creates anonymous user accounts which seem to merely pollute the server with inactive virtual users.
It is not entirely clear what actual use case justifies such a behavior of restoring anonymized backup and at any rate there are use cases which require assigning restored anonymized data to the restorer rather than to a new anonymous user.
The current backup/restore could be improved by making the owner of restored anonymized data a setting with the options 'restorer' and 'anonymous users'. Arguably, the 'restorer' option should be the default.
It may also be useful to allow access to such settings (in the final and root tasks of the backup/restore) through the plan api so as to make the creation of variant plans easier. An example would be a backup/restore from within an activity that needs to pass in the current activity cmid and omit the module info step so that the restore won't create a new course module.