I don’t have any extra drivers on my insurance other than myself so know nothing ? but looking at this wording from MB it seems like we were already able to, or it suggest we could already have 3 driver but they’ve just change the timing of when they could be added.
Quote from MB… “Following the change, you’ll also be able to add three drivers to your next application when ordering a new car. This is instead of adding two drivers when you’re applying and a third after collecting your new vehicle.”