Simply because Pirou is almost not known for a pornographic filmmaker, credit is usually specified to other films for getting the initial. According to Patrick Robertson's Film Specifics, "the earliest pornographic Movie which could undoubtedly be dated is A L'Ecu d'Or ou la bonne auberge" manufactured in France in 1908. https://felixcpajs.thelateblog.com/31334546/details-fiction-and-adult-sex