Got a reply from the person from the DNR he used as a source for the story. For anyone interested…
“You will find fishable populations of flathead catfish all the way up to Minnesota Falls which is located about three miles downstream of the town of Granite Falls. All of the Renville County Parks offer plenty of bank fishing opportunity with good flathead numbers throughout. Specifically, the area between ———- has some excellent water due to the large number of snags creating quality habitat for flatheads. Good luck!”
Hey, I can’t give my new secret spot away! 
So who is up for a little overnight camping trip?