What’s the difference between and actor and a movie star. An actor is someone who pretends to be somebody else. A movie star is somebody who pretends that somebody else is them.
With a historical novel you know that liberties are being taken. Since Walter Scott, we know that poetic license, dramatic license, that events been conflated and that liberties have been taken, characters ditto, dates rearranged. But people don't seem to understand that movies are fictions, they are dramatizations, at least historical movies, and we should accord the moviemakers some of the same understanding and latitude. When you go to a movie you know it's a dramatization and not history.
I think that the reason that people are so up in arms about movies that have historical inaccuracies is because now that we've trashed our education institutions beyond repair, people fear that the only people are getting their histories is through the movies, so the elephant in the room is that no one wants to talk about why we're so passionately obsessed with accuracy.
When you read a history or biography you are entitled to imagine that it is as accurate as the authors can make it. That research has gone into it and we say "This is a history of the civil war, this is a biography of Lincoln" whatever. But you don't make any such supposition when you say "This is a historical novel.
I was always a filmmaker before I was anything else. If I was always anything, I was a storyteller, and it never really made much of a difference to me what medium I worked in.