1. SAP Help Portal - S/4HANA - Down Payments and Down Payment Requests: "Down payment requests are noted items. They are not posted to a G/L account and therefore do not affect the account balance... You can also have the payment program pay down payment requests automatically." This source confirms that the request itself does not post to the G/L (invalidating C) and its purpose is to be processed by the payment program (validating B).
2. SAP Help Portal - S/4HANA - Process: Down Payments (FI-AP/AR): The process flow diagram and description clearly show that a "Down Payment Request" is created first
which is then processed by the "Payment Program" to create the "Down Payment" posting. This demonstrates the role of the request in enabling automatic posting.
3. SAP Learning - Course S4F10 - Business Processes in Financial Accounting in SAP S/4HANA: Unit 5
Lesson on "Down Payments Made and Received" explains that down payment requests are noted items used to request a down payment from a customer and can be processed by the automatic payment program. This distinguishes the request from the actual posting.