I thought you weren't an expert on alternative economies?

First, market socialism is socialism with elements from capitalism, so the particular mechanism (ad-hoc black markets) is a capitalist one, regardless of where it came from.

Second, in market socialism, the market is legal and "white". In North Korea, they are very much not legal - thus, "black".

Interestingly, the resilience of markets to pop up anywhere there's a need, regardless of legality or formal training in how to run them, tells us something about capitalism and it's inherent compatibility with human nature.