This is correct--at least with regard to legal sports betting. The purpose of the spread is to attempt to entice an equal amount of betting on both sides of a game. The house collects a fee, called the vigorice, (or vig for short) on each bet. The winners get their vig back, but the losers don't.
So...if the house takes 100K in bets and it splits evenly, so that it goes 50K in bets on Nebraska and 50K in bets on Indiana, and collects 10K in vigorice, then the house can't lose. They just pay the winning bets to the Indiana bettors with the money from the losing bets from the Nebraska bettors, give the winners their vig back and keep the losers vig.
The only way this business model fails is if too many bets come in on one side, and those bets go on to win. In that case, the loser money and their vig doesn't cover the winners payouts.
That's why lines change during the week. During the week before the Nebraska game, there was apparently a lot of money coming in betting Nebraska as an underdog at home against Indiana. So, they started moving the line, eventually making Nebraska a favorite to attempt to entice people to bet Indiana and even the money out.
I don't know if it managed to entice IU bets or not, but either way the house won, because all that money that came in on Nebraska early on ended up losing anyway.