Butkus is almost all reputation. I'm not saying he wasn't an all-time great, but we don't KNOW if he was. We don't have stats on him for tackles or forced fumbles or sacks. We have grainy footage and a bunch of guys saying he was intimidating. We have newspaper articles that built his reputation up.
I don't want to detract from how good he was, but we're lacking a big pile of evidence here. We just are. One must acknowledge that he was merely a pretty god or even average LB who played dirty. I'm not saying it's likely, but it's certainly possible.
What if he was a better center than a LB? We don't know that, either. There's so much we don't know - writers back then were all trying to be the next Grantland Rice, filling their columns with hyperbolic word salad, that Butkus and others benefitted from being built up in the minds of all the readers. It's as if Mickey Mantle was especially revered (as he is), but with no HR or batting average numbers.
All that being said, there's not exactly a ton of statistical evidence for a center in 1980, either, lol.