@donasmrs-- There was a need for the term "story arc" because a story arc is a continuous story or narrative. The term refers to television programs where the story continues from one episode to the next. That's why "plot" isn't the right term. When a film ends, the plot ends. But when an episode of a soap opera ends, the story arc does not end. It will continue with the next episode
So it's not really correct to use "story arc" for films, except for perhaps sequels where the story of the previous film continues onto the sequel.