All my backups are inside the same universe as what is being backed up. A boundary must be drawn somewhere and this is one of many reasonable boundaries. As I understand it, the backup isn't "inside" the volume but is attached to it so that deleting the volume deletes the backups.
Can we at least agree to draw the line so that if a single call can delete the live data AND all backups, they shouldn't be called "backups", but rather snapshots?