Thanks for the info here guys. For anyone with the higher trims (maybe all models?) there is a setting under either remote start, or convenience, that says turn rear defrost on auto. Perhaps many should turn this setting off and only use the rear defrost when needed, or sparingly, until we get more info.
I noticed one morning that while it was cold, my windows were clear, that the rear defrogger was on. So I putzed around in the settings and sure enough it was on auto-on. Could be related to having it run 10-20-30 min every startup