Had you charged to the room and settled at checkout, or did you just dine in and pay at the restaurant?
I would have assumed the hotel and restaurant have separate merchant facilities so Marriott offer only triggers when settling charges to the room account, and dining credit only triggers when settling at restaurant POS terminal. But if both restaurant and hotel use the same merchant facilities then I would expect it to stack...
I wasn't staying at the hotel at the time, so as much as I would have liked to charge it to someone's room, I paid in full at the restaurant
Come to think of it, one could really eek out some great savings by booking one night at the Ritz using FHR through the platinum card. You pay in advance with a travel credit. Then if you have the Marriot offer on multiple cards you hit up Hearth and Songbird.