The hotspot is how Android Auto works, you can do music streaming over bluetooth, but not Android Auto. It technically wont make any difference, except you cant use your wifi hotspot, and some Android applications arent updated to properly switch to cellular data when the wifi connection doesnt have internet on it. I am in the same boat as you, it just is what it is. If you do find a way around it, I am definitely eager to hear, but I havent been able to trick it in anyway.