Hi FLXPWR,
I found a reference in FCOM 1.70.20 pg 4 which refers to an N1/thrust lever angle 'keep out zone' however this, it says, relates to "on ground" operation;
" ......The EEC protects against fan flutter. In doing so the EEC prevents the engine from being stabilized between an approximate range of 60 % to 74 % N1 (depending on the OAT)..."
So this would seem to offer little in the way of explanation as to why the A/THR
does as you and I have observed in flight. :-)