You do not need to stop Qlik Sense services to get a backup of the Repository Database. PostgreSQL can handle queuing any transactions until the dump is complete. So the result is a valid .TAR file backup.
The concern with this method is that you really do need to stop services to take a back up of the apps used by Qlik Sense. Our Engine process does not queue transactions for a full restore you need a copy of the binary from disk + the DB from a single point in time for reliable results.