This is somewhat true. Also, while human beings cannot hear a dog whistle per se, due to the way the human ear works they can hear the beats produced by the combination of that sound with another, straightforwardly audible-frequency sound. Per Nørgård exploits this in his Symphony No. 5. But examples of this actually affecting enjoyment or even an A/B test in practice are so few they shouldn't really guide one's encoding choices, CD audio is already sufficiently wide in practice and claims that we need more are audiophile wishful thinking.
I'm definitely not arguing for the stupid "audiophile" frequencies. For the tiny fraction of music taking advantage of ultrasonic frequencies and high dynamic range it's nice there's an option now.
I hope the availability of high resolution, or more importantly the spacial audio, will inspire some artists to really explore the space. I'm hoping for some stuff like the Flaming Lips' Zaireeka or Yoshimi album's 5.1 mix.
