Title is misleading as it says 'oil' sales when article says 'fuel' sales.
There is a big difference as there are few refineries in North Korea for oil to be refined, so the country depends a lot on refined fuel to be shipped in for its uses. There just are not that many countries willing to do that, so that is the reason this is a big deal when China holds up shipping it fuel.
On the other hand, a number of countries, Iran is the biggest example, would ship crude to NK. Except, without the limited ability to refine crude, it does not little good.
I recall during apartheid no one wished to sell crude or refined products to South Africa. It made up for the shortfall by making its own fuels out of the abundant coal reserves it has, and Sasol became the leading producer of gasoline-from-coal in the world. Hitler did the same when the oil fields of Eastern Europe were closed off from him.