Richard D. Wolff

You are quite right; we use the terms as synonyms. "Worker coops" have a longer and wider use in the US. We ourselves invented and use WSDEs chiefly in order to stress the need for workers collectively to function as their own board of directors within each enterprise (office, factory or store). Worker coops sometimes get confused with or mixed into other sorts of coops (buyers or owners or sellers coops) so we often use the WSDE to keep them separate in people's minds.