What a great experience! He's joined us on the website for 7 full-length masterclasses, all available in the archives - www.jazzcomposerspresent.com/archives
One of the major pioneers of the second scale discussed was Alexander Tcherepnin back in the 1920s - in fact the scale is often named after him. It naturally arises from combining the two modes of the hexatonic major/minor scale (the first scale in the video), which Tcherepnin seems to have been somewhat obsessed with in his younger years. There's an excellent dissertation: "The Nine-Step Scale of Alexander Tcherepnin" (Veenstra, 2009) for those interested.