Illinois’s defensive players were calling out signals that were confusing the offense, which was a factor in the number of false starts.
Rhule is upset enough about it that he mentioned it to the media, which might get him a fine.
(FWIW, the officials in the Howard-Northwestern game did penalize the Northwestern defense for defensive signals designed to confuse the offense at least once yesterday.)
Officials are human and are thusly susceptible to errors like anyone else. I am not saying Illinois defense was calling out signals to attempt to confuse the Husker offense or not. It would seem odd that the officials would notice that and ignored it, especially if Rhule called it to their attention. My guess is the officials didn’t think Illiniois was doing that or just didn’t hear it.
What the defensive players say and how they say it are probably factors in whether it is flagged as deceptive.
Personally, I think there are some elements of it being fair game for the defense to try to say things that might confuse the offense’s, the offense has been using voice signals to get the defense to jump early for years. The counter argument is that the defense is allowed to move around trying to get an offensive player to move early, of course.