Since both engines initially responded to the autothrottle with increased thrust, that meant the restriction or obstruction was not in effect yet, at least not initally. Then within 3 secs or so, the right engine rolled back to EPR 1.03, with the restriction or obstruct in effect, with low fuel pressure present and HP pump cavitation damage taking place. The same sequence occurred for the left engine, although the rollback in power to EPR 1.02 occurred 7 seconds later. In other words the restriction or obstruction developed slightly later for this engine.
This suggests to me that the sudden increase in fuel flow required for the power increase, is what actually triggered the formation of the restriction or obstruction (whatever it was), which apparently was not present in the first few seconds of increased fuel flow.
I'm not sure what that means, but this appears to be the sequence of events. High fuel flow was available initially, then the restriction or obstruction developed (perhaps precipitated by the sudden increase in fuel flow), then low fuel pressure and HP pump cavitation followed and remained in effect until impact with the ground.
Of course the million dollar question is, what was the nature of the restriction or obstruction, and how could a sudden increase in fuel flow rates possibly cause it?