Nah, Sven. South Korea does use the 220/380V system as well as some old 110/220V system. They wouldn't bother installing Schuko sockets if there was no ground anywhere.
My guess is that what you are describing is their way of converting an old 110V two-wire installation to 220V: With just two wires and a center tapped 220V transformer, the only way to get 220V is to make both wires hot and conveniently forget about grounding... Unless you want to go for a full rewire, of course.
