As I understand, most films are shot in true 24p, and therefore I assume the original Star Wars movies were as well (especially given their age).
Your understanding, as well as your assumption, are incorrect. Very few movies, unless they are very early digital movies, were shot in true 24fps. Digital cameras today only have the capability of shooting 23.976 fps because early adopters of digital video in the film industry wanted the same frame rate as film, because they needed to print to film for distribution (very few, if any digital theaters in the early days of digital). The frame rate has stuck around because it has become synonymous with the elusive “film look” that people shooting digitally strive for.