Here are the instructions to winterize a Dometic 1350. They are provided in the Tiffin operator manual, not the Dometic 1350 manual. In fact, my Dometic manual only states that the ice maker should winterized by a service pro. Notice that you are instructed to remove both supply and outlet lines from the solenoid before energizing solenoid and blowing with air. This would indicate to me that we are only concerned with clearing the solenoid. Gravity must be all we need to make sure the ice maker is drained because you are not blowing any air ( or pink) up the outlet line through the ice maker.
I didn't bother with any of this. It was simple enough to just remove the solenoid.