Back in the 90's, when times were much better for us in "the rivalry", I know that my lifelong best friend and I - both raised in Ohio, but long time M supporters and alums - used to tweak our friends / families / alums who were OSU fans or alums by saying this. That is, back when M was routinely winning, we used to *LOVE* to say, "You guys aren't even our biggest rival! It's (insert ND or MSU)!".... Not that either of us really believed that, or thought that. But when we'd say it, it would invariably drive said OSU fan into a blind rage, about which we would cackle in delight.
I'm sure we weren't the only M people doing this to OSU folks. So, maybe it was a little of that too. Plus the Moeller thing in '94.
Go Blue - beat the Ogre Tech Buckeyes!