Actually, they didn't. They said that they had a "unique" strategy with him that would include hitting.
http://cincinnati.reds.mlb.com/news/...k_cin&c_id=cin
First of all, even a negative result is a result, and because he's transitioning into a starting pitcher, his status as a prospect has changed (for better or worse).
As far as his experience in the AFL goes, six starts does not make or break a minor league career when they were basically his first few attempts at starting since he was 12 years old. It's just too small of a sample size and too early on in his career. I wouldn't be shocked if he had a really up and down year this year as well as he basically learns how to pitch all over again.
Basically, I think the only thing that has changed about him as a prospect, in my mind, is that he has a new role as a starting pitcher, and that automatically makes him more valuable.