What disturbances are caused by the masses being off-center in the rotating satellite?
Two of the test masses define the rotation axis, and therefore can never be off-center. The others get moved to the rotation axis during the centering process, so they are also on center. The drag-free system provides all the forces and torques needed to keep the satellite’s rotation axis centered on the test masses. The remaining disturbance is just the drag free residual acceleration, which has to be dealt with anyway.
