Re: Not a problem - Not true
This is another version of erase on restore. The problem is that an old copy of a database can be restored WITHOUT applying the later transactions (and this may well be the case for debugging a problem) in which case the persons data is accessible again.
The question that the "right to be forgotten" legislation has to take into account is whether a commitment to delete a persons data if restored from a backup is sufficient.
There is also the problem that an old backup of a users files may contain personal data that was not identified in a search for such data because it was only in backups. (An example - a user had a spreadsheet with names and addresses that was deleted before GDPR came into force but which still exists on old backups.)