So I always make speculative bookings with cash and points to either earn stay credits or to apply DSU.

Today I called the diamond line and was told that since I did not have sufficient points in the account, I am not able to make the c+p reservation but am able to make the full points reservation without the points...
She even checked with her supervisor.

Currently, I have about three future reservations made without the points being applied but was able to as long as I have enough points by check-in. The agents who made these reservations said that it was okay since I am a diamond member.

Does anyone know what the official policy is?