This is absolutely correct. It was charged for both the cash and the Point room. Still awaiting reply to emails.OP clarified a couple times they had to pay the charge.
When it happened to me at another marriott property the front desk clerk said it was what Marriott paid the hotel for my point stay, no idea if it was true. Op only had 1 room on points, their cash room also got charged the fee. It’s literally on the bill like if they bought a meal at the hotel and charged it to your room.