Chris,
I think a green that is defined as featuring little in the way of internal contours, are those with a consistent slope, like a Redan, or a traditional back-to-front sloping surface. Therefore, you have a pretty good idea of the read on the upcoming putt.
Internal contours create more complex putting surfaces that may segment the green into smaller targets or tiers, and result in greater putting and recovery options because of the more varied surface of the green.
TK