On my wife's 2015 X1 you can turn the auto start on or off with a switch and it doesn't default back every time you start the vehicle - once off it stays off unless you choose to turn it back on . Not sure why every car with auto start/stop doesn't have such a switch. It also shows you how much auto start/stop is hated as there are numerous cottage industry products available that allow you to disable it if the vehicle came with it permanently on.
My wife and I both really dislike start/stop. If her vehicle had come with no way to turn it off we wouldn't have bought the vehicle even though we both liked it a lot. You'd think manufacturers would realize they will lose some sales over forcing this upon the public.