A380focal
The same would be true for any blockage to the fuel upstream of engine - it opens the valve more and more, but no more thrust is coming. The FADEC is confused in a way - but this does not cause a lack of thrust - the lack of thrust would result from the engine not getting fuel due to a blockage.
On this basis if the throttles didn't move in line with the FADEC demand the problem could have been quietly brewing for hours in the cruise without any indication to the flight deck crew.
During the latter part of the flight the fuel flow in the cruise would have been about the same as on final approach.
One other point we don't know how much cargo was on the aircraft but 130ish passengers would equate to about 12 tonnes payload. A 777 at a low weight could well be at or above FL400. Does anyone know the flight profile of the aircraft?