No, that promotion is offered by Marriott as part of the booking system: the hotel has no involvement in it. A hotel can't actually "merge" stays, the hotel staff are just checking you back in each day behind the scenes and letting it feel like one continuous stay even though it's actually multiple. I guess theoretically you could ask the hotel if they'd throw in a free night based on the promotion but the likelihood of that happening seems slim (especially given they try their best to make points hard to use).