I know this question was asked of TSOron, but I believe I know the answer, so I'll give it. I'm sure he'll correct me if I'm wrong.

The terms "enhanced" and "standard" pat-downs describe the same thing. They are used either in the case of an opt-out or in the normal case of an anomaly. Usually, in the case of a single anomaly, the pat-down is restricted to the area of the anomaly and very fast (a few seconds).

If the anomalies have a certain pattern (whose details are apparently SSI), relating to both position and number, then a resolution pat-down is required.