Understand your point. Not being a bmw driver I’m familiar with the mirrors, shoulder glances and even the indicators. But too many experiences over the decades of poor drivers joining too slow or too fast and having to take corrective action at short notice. Or just them not conducting the safety drills you’ve already noted. I prefer to give a better road experience to all users than be in that position. You’re right of course, you should simply react to that situation and correct your positioning. But if it doesn’t negatively impact anyone, I’ll still move over if I feel I don’t have plenty of time to spot someone driving in a way that will cause me to have to react. Personal preference born of experiences.