I found this on the T&C for the DL Platinum Amex just for example:
"Basic Delta SkyMiles Platinum American Express Card Members can earn up to $150 in statement credits per calendar year when a Basic Card or an Additional Card on the Account is used to pay for a new Delta Stays prepaid hotel or vacation rental booking on the Delta Stays platform (delta.com/stays) (each, an “Eligible Delta Stays Booking”)."
I also received a $200 credit on my Reserve card, but this was for a prepaid hotel.