I don't think he's stewing. He had plenty of great quotes over the offseason regarding where he stands in the organization. Paraphrasing here, but stuff along the lines of "Im going to work on my craft", "I dont mind playing in the minors because I'm not ready", and "If they do call me up, Ill be ready for it".
I don't think he expects that it's his time yet, and any struggles he's having are most likely purely developmental rather than him being "bored". All this boredom nonsense is getting thrown around way too much with Kopech and Eloy. This is Eloy's first full season above A ball. Kopech is in the middle of his 2nd season above A ball. These guys simply aren't ready. Eloy's not bored, he's slumping like all hitters do. Now he needs to prove he can make the necessary adjustments in AA, get hot again, and crush his way into AAA. Kopech isn't bored, he's just too wild still and has a lot yet to prove in AAA. He absolutely has to stop walking people, and I highly doubt his wildness is caused by an underlying anger that he's still in Charlotte and not in Chicago. MK seems too mentally grounded to have a bother like that.