In today's world when a movie says "based on a true story", it does not really mean much compared to movies of old. Where they used to take some liberties, now they just use the story as a idea and not the basis of the movie.
I cringe when I hear Admiral Yamamoto say, "I fear all we have done is to awaken a sleeping giant and fill him with a terrible resolve." in the movies "Tora, Tora, Tora" "Pearl Harbor" and now "Midway" (2019). Never!, has he ever said that in real life. No document, written records or witnesses. And yet, you might have been taught that in school, heard that in the movie(s) or somebody saying that.
I constantly argue with ppl on this specific subject.