Though we pointed up a discrepancy between the English transcript and German audiotrack of Groening's interview, it turns out, according to director Laurence Rees, that
the transcript correctly represents what Mr Groening said in his interview. He did say he had seen the gas chambers. But these words were not used in the final edited sequence of the film. Much fuller versions of Mr Groening's testimony are already available in published form in the book of the series which I wrote. On page 373 of the British paperback edition, for example, you can read a more complete section of his interview where he talks about seeing the gas chambers. It was this section which was edited down for inclusion in programme six of the series. Elsewhere, on page 207 he describes seeing the Zyklon B inserted into a gas chamber.
Unlike deniers, at least we publish corrections.