I agree that it's silly to try and search out a "perfect reproduction" of someone else's idea of how a song should sound, but if you were to do that, it would probably be the mixing engineer, and Harman is basically designed to mimic the sound of speakers in a room. So that kind of fits.

I also think it makes some logical sense to use EQ to smooth out the things that makes a headphone weird (e.g. a massive spike at 8khz), because nobody would mix/master music on the assumption of a bizarre frequency pattern that is idiosyncratic of a particular Grado (for example). The Harman curve is the closest thing to a "normal" that there is. Then from there you can adjust to taste, like by boosting the bass. Or maybe by adding back some treble if that's what appealed to you about the Grado in the first place.