I think the authors mean that binary way of looking at the texts mean that it only considers certain terms that mean queer. In reality you can't exactly label a person just one certain term these days. There are so many other categories of sexualities than just gay, straight, or bi. No one ever really talks about transgenders or even lesbians for that matter. Also no one even talks about the adjectives of these different types of sexualities such a flamboyant gay man or a butch lesbian woman. When it comes to the queer cinema reading they suggest that we as people are supposed to identify with the characters in the film yet there is such a small group of queer characters for queer people to identify with. The central character is usually a white male.