The important distinction is that the Mercedes does not demand the driver be paying attention and ready to take over immediately if the car decides to pop out of self-driving mode. Tesla does not offer that.
Are you sure about that? If it starts raining or the sun goes down, the system isn't going to alert the driver to take over?
You are guaranteed 12 or so seconds to take over. That means the system can handle anything, from moving over from emergency vehicles to unexpected debris while you take over