Am I right that a "Stipulation" is not a DRO even though it stipulates exactly what the terms are. It is signed by both parties, their attorneys and a Standing Master In Divorce (whatever that is).

Depends on what the status is under applicable domestic relations law. It could be a domestic relations order. A stipulated property settlement agreement, incorporated in a judgement, decree or order, or otherwise officially contemplated by applicable law and procedure and approved, is a common form of domestic relations order. If you had a judge rather than a Standing Master, you probably would not have a question. It is possible that a Standing Master has the appropriate authority under applicable domestic relations law to make it into an order. But beware Sitting Masters, Running Masters, and Masters with Bad Posture.