The only plausible reason would be to hide a defect. Not a factory defect but a ding or dent that the guy put in his shaft, filled in with super glue or epoxy and sanded down to hide the defect.
As recommended, use with caution.
There was a thread a while back about the Revo that snapped in half. The photo of the cross section of the Revo showed the side wall thickness to be extremely thin...maybe a millimeter or 2. Sanding down anything that thin will create a weak point in the structural integrity. I'm guessing the sanded Revo would eventually buckle at the weakest point.