The charts are calculated by taking a given instructor's mean for each summary category, subtracting the corresponding mean for the Norm Group, then dividing by the corresponding standard deviation from the Norm Group. This provides some degree of consistency when comparing the charts from one term to another. Here are several answers, each of which may be partly true. Take your pick. First, these are statistics, not Tablets of Stone From The Mountain Top.
Surprises are the norm.
You should view this as a guideline, not the Absolute Truth. The important point is that the CCR is seriously flawed from a statistical standpoint. Second, not everybody scores all the questions. Details of the analysis of the Norm Group are shrouded in the mists of time, and it isn't at all clear that they received the same benefit of the statistical doubt. Third, perhaps today's students just aren't as tough or demanding as the students of the early 80's, and they tend to go easier on instructors.