It's a global market. Europe needs X barrels, China needs X barrels. If China buys from the us, it isn't buying from Canada and visa versa. Extra supply benefits all buyers whether China or Europe.
But a barrel is a barrel is a barrel, anywhere in the world.
So if we sell to France and Russia sells to China, it's no different than if we sell to China and Russia sells to France -> the "same" oil ends up in the same place and the same money ends up in the same place.
They mean when China needs X additional barrels of oil, and they buy it from us, then they don’t buy those X additional barrels from Canada.