My only problem with this pick is that it conflicts with the basis of the system.

You reason, rightly, that handicappers know that the public tends to overbet ranked teams and especially so if the ranked teams is the underdog to an unranked team. Hence, they would only make an unranked team even a small favorite if they thought they were really going to kill the ranked team.

That normally makes a lot of sense.

However, the handicappers also happen to know that teams with massive nationwide fan bases like UNC in basketball and Notre Dame in football get overbet regardless of the line.

This appears to be a case of the line setters realizing that UNC will get overbet at home far more than Illinois will get overbet just because they are ranked. Hence, they make UNC the favorite in what should probably be a pick'em game.