C-15: No early release was requested or agreed

Why the request exists

Escrow ties up a seller working capital until the buyer confirms. That is a genuine cost to them, which is why established vendors sometimes ask. It is also the standard opening move of somebody who does not intend to ship, and from your side the two requests look identical.

Why a policy beats a judgement

You cannot reliably distinguish the two cases, and the cost of getting it wrong is the entire order with no recourse. A blanket refusal costs you access to a small number of sellers who insist on it. That is a much better trade than being right most of the time.

Declining without friction

State it as policy rather than as suspicion. It is not a judgement about that counterparty, it is how you handle every order, and framing it that way removes the negotiation entirely.

Why partial is still marked down

Agreeing with a long established seller is a lower risk version of the same action and it is still the action that removes your protection. It is graded partial because the outcome is usually fine, not because the exposure is different.