I always took it to mean this......
Some courses have round or oval greens which are tilted, but usually the tilt is in a predominant direction; this is done to shed the water......
A round green which is pitched from back to front, for example, has tilt, but no internal contours.
In the same vein, a round green with little overall change in elevation could have internal contours. A green like this would not require a predominant tilt in order to drain properly, because the internal contours could be sculpted to collect water in the form of catch basins surrounding the greens.
We've all seen these, your ball usually comes to rest upon a grate when it bounds to the bottom of a greenside hollow.
My two cents.......take it or more than likely leave it!!!