It still is, to this day. The United Nations/USFK/8th Army/CFC commander is, and always has been, an American Army general, since General of the Army McArthur held that position.
Interesting! Probably December, 1952, or January, 1953 I had a seven man ROK squad assigned to my artillery battery to integrate them into the American way of soldiering. Other units receiving them used them as gophers and general janitorial work. I actually interspersed them with my crews so as to learn, and they did. They also fell in love with American food. I thought the command structure would change after the cease fire and the ROK divisions would fall under control of their own government. Thanks for the info!