I used to think JEE's ceiling was a #3 center, so I obviously don't know what Pionk's ceiling could be. I'll try applying a ceiling only once he has an off-year, and the later that occurs, the better. That's also the difference between Pionk and Healey/Peart/Masters, so far. Each of them have had at least one year of regression recently, but Pionk has not.
Not sure if I shoulld count Kiviharju in there or not. He got badly injured, but does not appear to have been regressing before that, and has progressed well since. Kind of a gray area for me. Kalem Parker is in a bit of a gray area, too. If I were to list which Wild defensemen prospects I suspect may become something I would list Buium, Spacek, Jiricek, Kiviharju, and Pionk. Someone else may, of course, but if they do, I won't have seen it coming.