Pins drift....so.........
I have not seen one that cannot be removed. Best way is to set it up in a mill and plunge with an end mill where the pin is to within a few thousandths of the major thread diameter. The remainder of the pin will slide or fall out when you tap the side of the brake using gravity as your friend.
Another way is to spin the barrel in the lathe and machine down the OD of the brake where it is threaded on and you will eventually see the pin.
Casey