There are two types of "internal" headsets, semi-integrated and integrated. The former installs like a standard external headset using pressed-in cups. The difference is that they go into an over-sized headtube which allows the bearings to sit inside the frame. The latter uses built-in bearing races (either machined into the frame or a metal insert for a carbon frame) so the "headset" is really just a set of bearings. There are many different types of integrated headsets and they are interchangeable. It is this type of headset that Chris King cries about.