On the A320/A330/A340 with the autothrust engaged on finals you will see that the achieved N1 is considerably less than the TLA position (the blue circle is the thrust limit at the time due to the levers being in the CL detent.) When the thrust levers are retarded for landing you will see that the first large part of the lever movement simply brings the blue donought down towards the actual N1 being used. Until it passes below the actual N1 there is NO CHANGE in the thrust. So a slow, progressive closure of the thrust levers actually makes no difference to the thrust until the last part of the movement. The final part also disengages the autothrust.
I think this should explain to you what your instructor was trying to put across plus unlike more conventional aircraft, it is possible for the thrust to slowly rise in the flare if the lever closure is too slow.