What is differences between B-grade and unauthorized sneakers?

[yoppy-ya]

I know that NIKE will produce 20,000 to 30,000 extra pairs, some even 50,000 pairs if they assign a certain number (i.e. 50,000) per model for each factory to produce. Reason being is that they need this extra pairs to replace the rejected pairs after they fail to pass quality inspection.
According to this, B-grade means something shouldn't have passed quality inspection which means they were supposed to be unauthorized shoes, but passed the inspection somehow and were released to the market, then were found out that they should going to be B-grade. Is my understanding correct?