From a bit of an insider's perspective
I think the view of your statistical model is tremendous, but sometimes it can miss on when an organization is pushing forward a philosophy intended to help long-term success of their pitchers. That’s what the Braves have been doing with many of their "stud" arms. The focus has been on taking off a tick or two of velocity on the fastball to focus on movement and command of the pitch down in the zone, and pairing the fastball primarily with the change early in counts, using their breaking stuff as an attack pitch later in the zone.
That has led to a number of guys struggling with their control and giving up more than their share of contact, primarily due to that being a new approach for the guys new to the organization and in their first full season in the organization. There’s been adjustment to mechanics, position on the rubber, and other mechanical tweaks to help this primary focus as well. That would include basically all pitchers on this list outside of Povse and maybe Sims, so that makes perfect sense that Povse was the only one to work within the generated metrics you put together.
The guys I noted this strongest with were Newcomb, Fried, and Toussaint, and frankly, I’d be very intrigued to see how things would run if you ran their July 1st on for each guy as they each took some time to work their way into the approach and compared them to overall season numbers in your system. I’m not saying they’d suddenly grade out as plus, but I do believe you’d see a big difference.
The guy who has been teaching this in the organization is now working as the major league pitching coach.