Russia and Cuba? Why not mention Somalia and Afghanistan? They're about equally relevant in this context.

South Korea might have the capability to play this game (North Korea certainly doesn't), but it hasn't really had the incentive to.

Which brings us to the real issue: an export ban on an important product creates an extremely strong incentive, that didn't exist before. Throwing significant national resources at a problem to speculatively improve a country's competitiveness is a very different calculation than doing so when there's very little alternative.