“Based on a true story”.
When we look up to a movie that is based on true events, we expect them to showcase the truth, only truth.
But as soon as you change the story line which was supposed to be true, it no more remains a true story, not at all. Most of the movies based on a true story are not exactly what happened in reality. So it’s of no use stating that its based on true event. It should be like few scenes in movie are inspired by true events. I think that’s more appropriate.
Sometimes they cook story to make movie look too exciting or sometimes they will omit out things that will make the movie look bad.