Sometimes they say art transcends truth which reminds me that I must read Nazi Literature in the Americas by Roberto Bolano in which he explores how "literature is an unnervingly protean, amoral force with uncanny powers of self-invention, self-justification and self-mythification."
Here's the back story of The Diving Bell and The Butterfly. Basically, it comes down to this: the film does not reflect the truth. It's beautiful but untrue. Does it necessarily detract from the work? I think to say no would be lying.