Simple they don't have a normal reservation agent process to move "Reward" stays. It is a manual process and as several previous posters have indicated above. You need someone from the Swan & Dolphin in-house or call the specific phone number in the email you receive.And honestly, I don't understand the mistreatment of people using points. It isn't as if the points magically appear in anyone's account (beyond a single one-night 50,000 award if you have a Bonvoy Am Ex).
The issue with the points is the main Marriott system adjusts the number of points required based on the date of the new booking/modification. That's why it is showing 60K or 50K vs 40K when guests booked very early.
As I mentioned earlier pre-paid or deposit only reservations are easy to move to the Swan or Dolphin since the reservation agent(s) all are trained since it a normal "workflow" process. Moving Rewards is a "special" process and the agent has to be trained on the special process due to the delay in the Swan Reserve opening.
Dave