I remember reading that the id4 has a lot of independent controllers, which all have their own firmware. I think most people only think about the update of the infotainment software. But VW seems to be working on something that is similar to updating all phones, tablets, watches, Kindles, PCs, laptops, WIFI routers, printers, smart light bulbs, robo vacuum, headphones etc. in your household all at once with the added complexity that nothing works anymore if it's not done in the right sequence or any update fails. I would imagine that their are many power cycles and checks involved, which draws a lot from the 12v battery.