I'm going to disagree in Brieske's case and my logic is this: What he has to do is throw more breaking balls in competition but he can't go that in a major league game because he immediately gets behind and has to come in with the FB and get hammered, so he won't throw it. So he either stays in the game as best he can without getting enough work on the breaking balls, or he throws it and ends up quickly out of the game. I don't think this is the same thing as learning to sequence or learning ML hitters or even getting on top of his fastball more (Skubal last season). He doesn't really seem to have the pitches down at all yet, so Brieske needs reps doing exactly something he can't stay in games doing at this level. Maybe Fetter is a miracle worker but I don't see how he makes much progress, or at least as quickly as he could against better matched competition.
Sure, I hope he throws a shutout next time out, I just don't see how he gets there yet.