With your hand on the throttle there is no way you will forget to add (or reduce) thrust. Taking your hand off the throttle while hand flying is a mistake made only by pre-solo student pilots and rank amateurs.
That skydeity apparently forgot that he had disconnected the autothrust and expected the engines to spool up! He was looking out visually for the runway, manipulated the side-stick but not the throttles. Mental fog, possibly.