I think this is not that important. Even if they are different, they compete for the same arable land and for the same water and for the same labor to grow.
In other words, if the farmer grows "fuel corn" instead of the "food corn" you will still be without food corn, one way or another.
There is a shortage because regardless of what type of corn they grow for ethanol they still take up farm land that would normally be growing food corn. If a farmer, for instance, has 200 acres he puts into corn and decides to grow ethanol instead then that is 200 acres of corn not produced for human consumption of cattle consumption as the case may be. There is a finite amount of land for growing food, you can’t grow fuel on the land and expect not to lose production on the food corn.
I grew up on a farm and I know there is a difference between what we called “field corn” and “sweet corn”. The corn you find in conveniently sized cans in the grocery store is sweet corn. The corn that makes tortillas, corn chips, high fructose corn syrup, etc. is mostly the same stuff.
IIRC, my dad would plant different hybrids of corn for different uses. I believe the high lysine corn for the pigs, and a different variety for the cattle. What was left over from filling the grain bins and silos was sold. Once sold it went to the highest bidder, if not already sold on contract.
So, there is sweet corn and “field corn”, oh, and popcorn. For the most part the same corn used to feed cattle is used to make corn flakes.