Note: Having not noticed this app, I made a feature request for the Nextcloud core which is covered in part by the functionality of this app: nextcloud/server#17328
I would like to suggest that the app offers a configuration choice for where to store the backup files within the realm of the files app so the backup files can be pulled and moved to another location, e.g. a separate backup server or offsite-backup.
This is somewhat important for docker instances where stuff inside the container should basically be directly accessible only by the container.