I can’t speak for most of the crops listed, but I do have experience with members of the Chenopodium genus. Corn is a lot less work!
The researcher in the article compared yields, but not the man-hours needed to get it from the field to the dinner table. Corn doesn’t need threshing or winnowing, and you’re a lot less likely to end up with a ton of chaff in your lungs.
I’ll agree that it’s less work, but I have lamb’s quarters growing wild in my yard and it’s a lifesaver for me. The leaves are edible, do everything culinarily that spinach does, AND they dry for use over the winter. I’d be all over that even without the seeds.