"Based on a true story" is a come-on, the aesthetic equivalent of "no loan request refused." For, at best, the creator has fashioned a film based on his understanding of, interpretation of, and reduction of the report of an actual occurrence.
David MametThe audience will teach you how to act and the audience will teach you how to write and to direct. The classroom will teach you how to obey, and obedience in the theatre will get you nowhere. It’s a soothing falsity.
David Mamet