I don't believe the FAA is saying that TERPS is NOT TO BE USED for OEI. What it is saying is that is does not have to be, and is usually not by many aircraft performance charts.

Running your all-engine data for an FAA certified aircraft does not automatically give you obstacle clearance in the event of a loss of one engine. If your OEI performance still guarantees the required climb performance, you are golden. For many operators, we run all engine performance then reference a special engine out departure procedure that gives us a obstacle cleared flight path to follow in the event of an engine failure. If our data was for engine-out, we would not have to reference that page.