From what I’ve read, you aren’t protecting your freedom when pairing a smart phone to a rental car. Maybe so if you know how to clear it out before returning the car..
1. I never ever download all my contacts to a rental car. It’s always an option when you pair it.
2. I usually forget to delete my phone from the rental car when I return it. In fact, I usually delete from one to three previous phones from earlier customers. But there’s no way I’ve found to view any of their information. At least no way I’ve found.