I haven’t been able to find this through iOS but maybe the car has an option in its setting to change the name of it. Looks like it maybe takes the name from the Bluetooth list and it’s absolutely ludicrous that iOS doesn’t allow you to rename Bluetooth devices in 2020. At work, we have a fleet of about 30 Ford Tauruses/Explorers and 10 Dodge Chargers and I have no clue which Bluetooth profile belongs to which car. Just says Sync and U-Connect in a very long list. Absolutely ridiculous!
Bluetooth names can only be changed on accessories sophisticated enough to support it. This requires hardware and software more then a standard receiver would have. Proprietary in some cases...
OS's that support name changing (aka bluetooth friendly names) are still seeing the default name they are just showing you what you want to see. The name change only applies to the device that changed it. MAC hardware address is used to identify and rename the hardware locally.
For privacy iOS uses a UUID for BT in place of MAC address to mitigate tracking done by scanner. I believe this makes renaming devices less reliable though (which is already not very reliable as firmware updates and sometimes reboots can revert to the default name).
To actually change an accessories name it needs to be done via the accessories or its software.
