I saw a picture posted here, but cannot find it. You lose a lot of trunk space as the spare just sits on top of the trunk floor since the battery is there. There is also some plastic to hold it in place and creates a small cubby or two.
Edit
These arent the pictures I saw originally, but you can see how much space is lost
https://www.bmwblog.com/2019/04/08/b...king-delivery/