not intended for direct human consumption

Certainly. But it's still edible. Dent corn, for instance, can be and is used for cornmeal, masa, tortillas, and so on. The industrial monoculture varieties of dent corn are optimized for animal feed, ethanol, or whatever, but nothing's stopping us from eating them (except, in theory, the ridiculous amount of herbicide and pesticide that gets dumped on them).

The reason why we're growing so much corn that's not intended for direct human consumption is because of a whole shitload of broken incentives and megacorporation subsidies and America's meat addiction and the nagging worry that if we don't keep the land in use we can't justify stealing it from the natives however many generations ago.

Which is part of what the article goes into.

And it's why the idea that ethanol opposes Big Oil is so ridiculous. Ethanol and Big Oil go hand in hand. Their interests are aligned and Trump loves them both.