Well, think about it this way. In any airplane, do you start the engine on the ground with the avionics master on? If you are using the starter to get the prop unfeathered, that's going to be the same high draw on the battery and you are repeating the situation on the ground that you have the avionics master off for in the first place. Cranking the starter.

That said, in my old Apache, the avionics don't shut down when I use the starter to unfeather the prop, and I don't turn the avionics master off, either (maybe I should).