MS can also reallocate points on existing reservations. So for example if a mistake is made or you cancel a reservation you can then ask to reallocate points on another reservation in order to use all banked and borrowed points before current UY points in order to bank them.
A few notable points:
- you cannot reallocate not-home-resort points if you used the home resort booking window (example: you book at 11 months using BCV points, then you transfer SSR points in; at 7 months you cannot reallocate SSR points to the reservation)
- if you bank/borrow points to make a reservation you cannot "unbank/unborrow" them.