Some devices come with apps that include proprietary renaming features. Those devices can be renamed.

Your iPhone's rename feature won't change anything for other devices. Maybe Apple is smart enough to sync the renamed device to other Apple devices as well, I don't know about that, but it certainly won't change what the other passengers on your phone see.

You can distinguish Bluetooth devices by their MAC address, that's usually how the rename mapping works.

iPhone BT settings also let you rename devices, but I think that's just a local setting, not like the BT spec has a rename feature. Not sure cause uh, my iPhone broke. But for sure there are speakers that have their own apps that let you rename them.

> I know for certain if you change the setting General > About > Name in an iPhone it changes what everyone sees when they look at their list of available Bluetooth devices.

> I assume other Bluetooth devices are the same, no?

No. The iPhone is allowing you to configure what name it broadcasts. But you cannot just tell another device what to broadcast. That device must have its own mechanism for changing its name.

For example, many Apple wireless peripherals can rename themselves after your user account once you connect them at least once. That has to be a function of the peripheral though, it's not performed by the device you connect it to (past telling the peripheral the new name, of course). Third-party peripherals usually do not have this functionality.