There is no such thing as corn gluten.

Question

You can purchase gluten( usually wheat) and different milling of corn med. fine and flour. I am confused when your article refers to “corn gluten” as one product

Answer 1

Yes, Corn Gluten is available and used as a pre emergent.
This link from the University of Iowa has more information for you.

https://www.hort.iastate.edu/horticulture-research/corn-gluten-meal-research/