In defining the acceleration performance of an engine, the designer looks primarily at a couple curves:
1) the steady-state line - what fuel flow will cause the engine to stabilize at a given speed?
2) the stall or surge line - how much instantaneous increase in fuel can the engine tolerate before the compressor goes non-linear?
He then creates an acceleration fuel schedule that is close to, BUT NOT ABOVE, the stall line. That way, when the pilot calls for acceleration, the control can predictably deliver that acceleration without stalling. Whether a mechanical or electronic control, it makes no difference; the principles are the same.
But what happens when the engine aerodynamics are degraded (FOD, sand erosion, avian attack...)?
First of all, the steady-state line moves UP. More fuel is needed to hold a given RPM. This is the natural result of poorer component efficiency.
And the steady-state and accel schedule lines may not be parallel. The steady-state line may intersect the accel schedule - who knows at what speed? It may be 70%, it may be 35% - the fuel control still is programmed to avoid compressor stall, and that's the limiting speed for the engine in that degraded state.
So the engines (as I see it) WERE NOT at a governed, stabilized idle, even though the gages might have suggested that. They were trapped by their degraded steady-state line intersecting the accel schedule.