Who knows. Something as minor as that one is usually ignored, as well as the one (and I can't recall the specifics of it, just that it was extremely ticky tack, just like that one on Utah) that had been called on BYU earlier.
B12 refs have been ignoring holding penalties this year. Maybe the coaches were starting to get on them for not calling holding because it was becoming ridiculous. These two calls look like over corrections.