I don't know...
At around 500 Hz, a half tone difference is about 30 Hz (more or lees roughly the smallest difference between notes in Western music). This is testing small fractions of that, well below quarter tones and anything used in other musical systems.
Music is about pitch relationships (covered here, but mostly with differences much greater than tested here), rhythm*, dynamics*, harmonic composition* (for one instrument, this reduces to just the timbre of that one instrument), and so on.
*all not tested
For evaluating audio reproduction quality, I don't see too much relevance either. I suppose if you also have amazing pitch memory, then maybe you'd be able to notice some playback systems not running at the correct speed—e.g. Sansa Clip+ being something like 0.25% fast, so 500 Hz is like 501.25 Hz (all frequencies likewise shifted, so no change in musical content).