I'm not sure it's as simple as creating a 19+ section for twitch. All Korean sites need an ID for users to register and this is done to track and verify people's age. As far as I know, Twitch Korea does not need that (I could be wrong here). If Twitch does establish a 19+ site, due to minor protection laws in Korea, twitch korea would need to comply with this. I'm not sure if Twitch is going to be willing to do this extra step just for korea. If anything, korean twitch will likely just not have access to 19+, just like how they lost access to vod and 1080p.