What might possibly be confusing is the language regarding Delta co-branded credit card "stay credit" (amount varies with card choice).
That language does specifically mention "prepaid" rates (e.g., this from the Gold card site)::
$100 Delta Stays Credit‡
Elevate your travel experience with an annual statement credit of up to $100 after using your Delta SkyMiles® Gold American Express Card to book prepaid hotels or vacation rentals through Delta Stays on delta.com.