Just had a thought.....

The E38 stays "alive" for a long time after ignition off.... if you don;t open the drivers door! I think the time mine kept logging was when the missus went into a shop to buy some stuff while I sat in the car. So the drivers door never opened and all accessories kept running. I bet this is why the ECM didn't stop sending data. In this case, it's actually a good thing as you can log IVT cool down rates etc once the engine has stopped.