de0u I am not an expert, but I think "nearby devices" covers not just establishing a Bluetooth link with a previously paired headset, but may also cover listing paired devices, scanning for unpaired devices, etc.
That might be true. I don't know.
If you and others are placing phone calls using a messaging app and a paired BT headset, would you mind checking I you granted the "nearby devices" permission, just to see, if it is really necessary to have this allowed. In my case the BT device is already paired.