I dunno, I dunno. Dumb is one thing, like it's absolutely a fun aspect of a character, "strong and charming, but rather dimwitted." That isn't really what a 6 corresponds to though, within the ruleset, hell within the simple bellcurve math and distributions. A 6 is more like severe learning difficulties. It's straight up mentally handicapped. "The disabled fellow with the big smile and muscles." I assume Dan's image of his character is that of an uncomplicated, simple-thinking bruiser with high aspirations, but he's ended up with Hodor dressed in silk robes.
Distributions showing natural three dice totals, and the 'heroic' equivalent values that they used, with 4 dice ignoring the lowest. 6 is
reaaally low, it sits easily in the extreme outlier realm of things.
Which, don't get me wrong, isn't to be all stiff and claim this shit is super-important; Rorie is free to use or interpret all of these numbers as best suits the story. And I've no doubt he will. But it's arguably simpler to just ensure that everyone's stats sit on the in-world scale at a realistic and roleplayable level. Bumping the 6s to 8s won't stop those characteristics from being sucky, but the numbers will at least crossreference against other NPCs more nicelier.