Chinese lockdowns are the most extreme form of social distancing -- everyone in Wuhan and similar hotspots stays home, not just ones for which there's some reason to suspect infection. In South Korea and elsewhere in China, there's special attention to quarantining people who are starting to show symptoms, and close contacts -- but there's also substantial social distancing as well (closures of schools, museums, retail...). There are examples where quarantines have been part of a successful strategy, but it's hard to find one where they've worked with no other elements.