Answer
Yes, Hwang Sun-hong has indeed managed adult teams. Prior to his current role as the manager of the South Korea U-20 national team, Hwang previously served as the head coach of Ulsan Hyundai Mipo Dockyard Football Club, a professional football club based in Ulsan, South Korea, competing in the K League 2, the second tier of the country's football league system. He held this position from 2018 to 2020.