As always, it is impossible to explain a scene the way Jo does in the books and due to changes in the past (for example: S.P.E.W was never even mentioned in the films) certain scenes have to be made differently. True, I don't see why Harry couldn't be present but after all, changes have been made in HBP and still it turned out awesome. So I suggest that people chill and let the directors do their work.. after all it might turn out even better than in the books ;P