I still think that is some misguided information. With the mast rotated fully, it's putting the major axis of the mast closer to in-line with the spinnaker loads. We always get nervous if it under-rotates. Distance racing on the I20, we used to sometimes run a positive mast rotator to make sure the mast didn't under-rotate.

Is it that they are saying that the boat is faster by not rotating the mast to 90 degrees with the spinnaker up?