Actually, The Atlantis Bahamas resort is now part of the Marriott Autograph Collection, and the Cove, Coral, Royal, Reef, and Beach all can be booked on Marriott.com and have elite night stay credit according to the rewards desk. I asked platinum rewards desk if the can escalate why Harborside is not on the list even though it displays as part of the autograph collection here:
www.atlantisbahamas.com/rooms/harborsideresort
but is not listed here:
www.marriott.com/atlantis/travel.mi
I think owners should get elite night stay credit per the August email from Vistana that states: "For the first time ever, Owners will now earn credit on their ownership stays toward higher membership tiers in the new loyalty program (Platinum Elite, Lifetime, etc.)."
...Note that this does NOT exclude Harborside...
The Marriott Rewards T&Cs has a section covering Atlantis that does not specifically exclude Harborside or elite night credit.
I stayed at Harborside for 20 nights and was on the phone with the platinum rewards help desk for over an hour. They were helpful but cannot give elite night credit for Harborside because it does not have a hotel code in their system. The other Atlantis hotels do have Marriott hotels codes. You will have zero chance of getting elite night stay credit for Harborside until it has a hotel code.
If anyone is a Harborside owner and has contacts with the owners association, I suggest they raise this issue and see if Harborside can be assigned a hotel code in the Marriott system. The combination of it being a Vistana property and the other Atlantis hotels being in the Autograph collection make a good case for adding it. The rewards desk rep I worked with has sent an email to management, but I wouldn't count on it being corrected just from an email.