He's obviously not going to say that any Braves prospect's floor is a guy who never contributes anything. These guys will read this stuff.
My guess is that he means that a reasonable low-end projection for him, given his current abilities, is Kevin Pillar. I don't think there's ever been any prospect in baseball history in A-ball who didn't have an absolute floor of 'never contributes anything at the major league level.' Obviously Kiley knows that.
What Pache does have is apparently incredible athleticism and defense. Sure, it's possible he doesn't get to Pillar's level. But Pillar was a major league player who made it almost entirely on defense and athleticism. So even if Pache doesn't add anything else to his game, he can get to a level like that. I'm pretty sure that's what he's saying.
I suppose I misread, “if doesn't improve at all he's something like Kevin Pillar”, to mean something other than describing his low end projection.