What we hear is the artist's vision of their music after the mixing stage. Without hearing the raw mixes, anything else is speculation. Am sure there are many justifications advocates could find for seeking a flat frequency, but "hearing the music as it was intended" is a misapprehension if nothing else - unless one is the artists or involved in the production
Never said hearing the music as it was intended. It's hearing the sound file faithful to the source (whether or not its the way it was intended is a different story). EG, hearing the sound as the sound engineer does.