"Security through obscurity" is a weak concept, however the goal here is not security but fraud detection.
Obscurity is a legitimate component of a fraud detection system, for the same reason that hiding your cards is an important part (but only a part!) of being a good poker player.
Obscurity is a legitimate component of a fraud detection system, for the same reason that hiding your cards is an important part (but only a part!) of being a good poker player.