So, to be fair, I never said I was out on Mathis. What I said was "I'm not super enthralled by the super-passivity" and then explained why, then showed when asked where there was any reason to believe he was super passive. There's a lot of ground between "out" and "I think the best version of this player is elsewhere" and Mathis' data is probably hiding that issue to a decent degree. It's that I think as he graduates level over level that this passivity will be more easily exploited but at High-A I don't trust pitchers that much to really exploit these things consistently.
For example, I'm going to go back to the hitter I also brought up, which is Pete Crow-Armstrong. At South Bend and Knoxville, Pete kept his K% under 25%: that's a good thing. By Double-A he kept the K% the same, doubled his walk rate, and kept an ISO of .238. But what was hiding under that the entire time was the hyper aggressivity. Even last year Pete kept an 82% zone-contact rate; But eventually, pitchers get better and take your hyper aggressive ability and help you get yourself out.
Cole Mathis isn't hyper aggressive. And you're right, today, the K% seems to be the one thing suffering. But the passivity he shows is something I very much think will be something that better pitchers (and pitchers more capable than High-A arms) will use against him. And I think that's a point of polish for Cole Mathis, especially considering he isn't likely to make his mark on an MLB team in very many (if any) ways outside of the bat. And clearly I'm not the only who who thinks that, as Eric Logenhagen pointed out the same thing.
While I won't put words in your mouth, you may be of the "well it's not a problem today so I'm not sure I'm going to worry about it" mantra, and that's fine, it may be a concern about nothing. But the counter to that is being pro-active and finding a polish and working on it before it becomes a problem, as well. And I'm going to fit into the latter ground myself. It's also fair to point out the argument against that to that is "maybe you fix what isn't broke" (my argument to that would be he's running elevated K% at both South Bend and Myrtle this year and while it's just May 8th, I do believe that's an early warning sign - but I'll refrain from having a fictional back and forth here).
Honestly, I've been fairly high on Mathis dating back to the draft day. I like Mathis today. I think I can both like Mathis and point out a point of polish going forward for him. As we see today, when Pete Crow-Armstrong is the best version of himself at the plate, his hyper aggressive attitude seems to melt away for a bit and the guy we all wish he could be every day comes out. Much like that, I'd like to see Mathis trend a bit more in the other way; not because right now he's necessarily struggling at South Bend but as I feared with Pete in the same way; the concern is that better pitchers will be able to exploit this more often. And better pitchers did eventually exploit Pete Crow-Armstrong's hyper aggressivity and the solution has been "be more controlled". While different, I think Mathis probably needs to come back to the goldilocks zone to find the best version of himself at higher level, too.
As it pertains to Kepley; I've mostly stayed out of Kepley Mania. I'd rank him higher than Cole simply because I think his path to MLB relevancy is easier with position. defense and speed in his favor, but I'm lower on him than many on the board. Not really all that important but did want to address that point that I think was more "to the world" and less "to me" but wanted to be as clear as possible, too.