At no time that I am aware of did the NEC allow 10/2 NM to feed a dryer.However if you were to use the 10-2 cable than the white would need to be re-identified as per 200.7(C)(1).
Originally posted by iwire:
250.140 exception (3) The grounded conductor is insulated, or the grounded conductor is uninsulated and part of a Type SE service-entrance cable and the branch circuit originates at the service equipment.The rules allowed using the neutral to ground the frame, the neutral is required to be insulated.