Not surprised by this at all. Unless the vehicle was traded into a dealer of the same brand, most aren't going to know or know how to "clear" this.
There's certainly no standard for this and this will vary by dealer. How many people have bought used cars and the previous owner's Bluetooth phone details were still loaded ?Alot of companies mot just Tesla are guilty of not wiping personal information even though it's supposed to be part of the reconditioning process.