Too many questions left unanswered. Your World Trade Center example just doesn't fit. There is no comparison. The events, as is typical of American fast and simple, are compressed into a few minutes whereas the long, drawn out days and months, and years of The Pianst just beg for explanation. World Trade Center is visceral, action-oriented, thrilling, popping action of the terror and horror of war whereas in the case of The Diary of Ann Frank as well as The Pianst we are looking at the lengthy period of the traumatic exposure to Holocaust. The audience isn't interested in knowing what they themselves think, the audience is interested in the character. How do events impact the character not us. What was the character thinking? What was happening while he was sick during the lengthy time in bed. What thoughts were going through his mind? How did he think? What were his emotions? What was his reasoning and how did they deteriorate. The surface features as just that superficial without the supremely unique feature of human thought and feelings. Each person is unique. If the picture were about animals, a voice over wouldn' t be necessary, because the dog or cat emotions and surface features are all that really exist and count. But even the focus is on a singular individual over the length of this movie oer a period of years, the inner most spirit of the human mind is what makes this movie truly special and without it, The Pianst becomes more an empty shell to be filled in with everyman's experience - not too inspiring project then.