If they did, I'd like to see that recipe. It's really hard to make beer from corn. You can make whiskey from corn, but beer is made from mainly barley.
They may be calling any undistilled alcoholic beverage "beer."
Chicha, the Inca beverage made out of corn is an example.
It wouldn't pass the German legal standard for beer, but it's sometimes called a "corn beer".
Kvass, the undistilled Russian beverage made out of fermented rye bread may be another example.
“You can make whiskey from corn”
The enzymes necessary to change starch to sugar are not found in corn. The corn mash must be combined with malted barley in order for all of it to be converted from starch to sugar. There’s no such thing as whiskey made entirely from corn.
Ever have corn wine?