i've havn't noticed kernals ripening at different times. my interests are in breeding a flint corn that drys down before the heavy fall rains that has excellent flavor. I have noticed dry down times vary. in gardening there are always so many variables it is hard to discern which one is causing which thing to "act" in a certain way.

I don’t have more experience but I agree with your intuition. I would suspect the seed ripening rate to be governed by the mother plant characteristics. However ripeness uniformity across the kernels would also be a characteristic of the mother plant. And I would suspect a mother plant resulting from a cross could introduce a change in that uniformity. I’ve heard other things like not to grow water melon near cucumbers because they will cross and your watermelon will taste like cucumbers. Clearly that is relevant for land races, and I suspect the wisdom is old from a time where more people were practicing saving seed. But atleast how that advice was passed to me ( that it will change the flavor of this years crop) I think is actually false, again the fruit properties should follow the mother plant. Because the genetics of the cross are in the seeds not in the fruit. The fruit is the flesh of the mother plant. This is how apples are.

I just got done reading Joseph Lofthouse's book about a month ago. I want to start a landrace or two of something easy after reading it. I believe he is still active on permies.com

My guess is the plant has more influence than the individual kernel. That makes more sense in my head. Lol

https://news.wisc.edu/corn-that-acquires-its-own-nitrogen-identified-reducing-need-for-fertilizer/

Individual kernels may contain different genetic information, but the ripening of the kernels (and other physical aspects of the cob) are mostly controlled by the mother plant. Think of it in animal terms - each kitten in a litter may contain different genetics from its siblings, but they're all born at the same time.