I don't know which Boeing you're talking about, but as a matter of principle any fault requiring the reduction to idle of an engine I would treat as an engine failure and fly the aircraft accordingly. If you are at cruise altitude and you have to idle an engine, clearly you will have to descend anyway.
I have encountered a similar situation in a bizjet where the engine was left running at idle thrust (due to an Engine Control unit failure creating surge like symptoms) but the aircraft was flown using single engine procedures for approach and landing.
On the 737 the ENG OUT CRZ isn't executable anyway, but merely gives information.