But it hasn’t been made “absolutely clear.” Just because the phrase is used falsely does not mean that it is a false statement in all movies. Besides, naive viewers still abound and it will not be absolutely clear to them.
It took a while for me to convince my students that The Autobiography of Miss Jane Pittman was not an actual autobiography and could be found under “Fiction” in the library. Yet the title wasn’t meant to deceive, as far as I know. Something similar happens with “Based on a true story.” But sometimes it is intended to deceive – especially at the beginning of a horror film.