To be clear, Avengers: Endgame was officially released in 60fps. The film was shot for the standard 24fps presentation. Therefore, a "60..." file is almost certainly a fan-created version where motion interpolation software has generated artificial frames to double the frame rate. While some viewers enjoy the "soap opera effect" for action scenes like the climactic final battle, purists argue it destroys the intended cinematic artistry and creates unnatural artifacts. Understanding this distinction is crucial: you are looking at a retooled, non-official version of the film.