I actually JUST saw this for my recent flights in my KE app. However, don't hold your breath for it to work. It takes your miles instantly, of course. And, considering they only release 3 biz class seats, and like my flight ICN-ATL and back was 100% full in J, I wouldn't expect any luck. Economy even was slam full for my flight.
it seems BRAND NEW and I even checked some Korean sites and didn't see much about it discussed.