This is really good move. For majority of users 12 cores is more than enough and not only will the architecture gains from 5-6 give more IPC but also gives the benefit of reducing latency by not always needing to cross CCXs for models with only 1 CCX. Assuming that is they don't do a 6/6 split.
Games right now are very GPU bound. So it won't benefit gamers to much but it'll definitely help streamers and recording users.