erm... either you shield all radio at which point, yes, you can't be tracked, but you can't make a phone call either. Or you don't shield the radio in order to make a call, but then you can be tracked.
Where's the flaw in my reasoning?
Because the people of North Korea will love the shapes and colors of the phones, and not the possibility of it bringing them out of poverty, right?
As the BBC article notes, production was probably in China. The "inspection" at the NK factory was probably more for internal PR than for any practical reason.