Jerry,
It still works out that the error distribution is "normal" because the attempts to equalize the betting on each side of the spread refects the knowledge of the "smart money". What it means is that there is a 67% chance that a game will be within 14 points of the line. Well, that's sort of a lot but the interesting thing is it is symmetrical about the spread. It's still the best bet.
The same thing happens when one used a mathematical betting system. such as Massey ratings - see
http://www.mratings.com
The errors are distributed normally because the error in the predictions is reflective of imperfect knowledge and chance with an equal amount on each side of a bet. If enough people catch on to a new idea that is a better predictor than the spread, the spread will move to reflect it.