Indeed, but not only is it not a tritone, it is (to my knowledge) not "diabolus in musica" either (that's also the tritone). The author noted the original error

Indeed, but not only is it not a tritone, it is (to my knowledge) not "diabolus in musica" either (that's also the tritone). The author noted the original error, but then corrected it incorrectly. :-(