Should RF be an SLD?

Jack Fletcher argues in his book, Learning Disabilities from Identification to Intervention, that subcategories of learning disabilities are arbitrary, and that based on what we know about learning, Reading Fluency should not be an SLD because all areas of learning require automaticity. Meanwhile, reading fluency across the nation is lacking proficiency.  Considering reading fluency in this current climate may be a serious lack of consideration for these trends in general education.