No, the distinction is between reactionism and populism, the former being right-wing and the latter being left-wing. Right-wing movements are classified as movements that seek to concentrate power in the hands of a few, and are either reactionary or establishment but are never populist. An example of a populist movement, given in the article, are the agrarian social movements and progressive political parties in late 19th century America. They are against the concentration of power and seek to bring about greater circulation of power and thus are populist and left-wing.