That response seems to satisfy the the powers that be in the dispute system,
There are no powers that be in the chargeback and representment process. You file a claim via the chargeback, the merchant then can represent. Visa/MC do not evaluate representment documents. The merchant is hoping that you drop the claim regardless of the quality of the documentation provided so they don't have to accept financial liability which is why you have the prearbitration bow in your quiver. If they know their representment documentation is garbage, they won't proceed to arbitration because they know they'll lose.
Chargeback and prearbitration fees are the cost of doing business for the issuer. You are more than compensated via interchange fees you receive when your customers use their cards. In the MC Rights and Responsibilities section of the Chargeback Guide
it notes that you must credit the full amount of the chargeback to your customer.
"When an issuer has billed a transaction to its cardholder's account for payment and then chooses to exercise a chargeback right, the issuer must credit the cardholder's account for the amount of the chargeback."
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