I had never heard of this concept before seeing this article. Great to hear it's in Germany also! Would you know if there is a list of co-ops in Germany somewhere, to see if there is one closer to me than Karlsruhe?
There are two things named Cooperatives: One is a coop that is owned by those it serves, e.g. a housing coop is owned by those who live in the flats, a food coop is owned by those who buy the food. The other is the coop as a legal form of corporations where you have essentially no difference between a regular corporation, a LLC or a cooperative, and the cooperatives will usually own other entities with different legal forms for actually run the business.
ReWe is the latter, and has nothing in common but the name of the legal form with what is discussed here.