A similar thing happens with comics; The New York Times's review of Art Spiegelman's WWII memoir "Maus" started with the line "Maus is not a comic".
This was meant as praise, because "obviously", if it's any good, it can't be called a comic book. (Then, of course, the term "graphic novel" got traction, and immediately got misused so often that it's now completely meaningless.)