I think Chapman is as advertised. He hits 100 with his FB but struggles with off speed pitches but that doesn't mean we throw him in the bullpen. They need to develop him as a starter because starters are far more valuable than relievers. It wouldn't be unheard of to kick off his big league career in the pen. They did the same thing with Mario Soto and Jose Rijo and the Rays did this as well with David Price.
Chapman's skills would be wasted as a closer. He needs to control his off speed stuff just like Randy Johnson and Nolan Ryan before him. He is not ready for the bigs yet. This is not news.