I am the OP, and actually, I just reject this explanation. I have always been fascinated by betting odds, and I can tell you with surety that this notion of "equal betting on both sides" is somewhat of a myth. Books set the lines, first and foremost, where they think the actual score will be; they do move the line sometimes to hedge their bets if they're afraid they will really take a huge beating, but the line is almost always set within 1-2 points of where computer advanced simulations project the mean score.
There are examples all the time of lines that were set despite knowing that bettors would overbet on one side. Last year's Super Bowl is a prime example, and a good majority of the betting came in on the Giants. Vegas knew this would happen but put their faith in long-term probabilities, which is that the Patriots win that matchup 55-60% of the time, which was consistent with most simulations. Vegas lost that bet, but they are correct 55-60% of the time. Had they really wanted to get equal betting, last year's Super Bowl would have been a pick 'em. The emotional sentiment was clearly with the Giants.