The only mention of corn in that Wired article is a concern for the height (since corn grows tall).
Height, too, is an issue: Corn and wheat would need taller panels, while shrubby soybeans would be fine with a more squat variety.
Thanks to those gaps, crops grown under solar panels aren’t bathed in darkness. But, generally speaking, the light is more diffuse, meaning it’s bouncing off of surfaces before striking the plants. This replicates a natural forest environment, in which all plants, save for the tallest trees, hang out in the shade, soaking up any sunbeams that break through.