Embrace the 2nd and 3rd harmonic distortion at low levels is the message. If you don’t like the message then move on.
Someone, please correct me:
I don't believe that the idea is to "want" 2nd and 3rd harmonic distortion, but rather our brains use the 2nd and 3rd harmonics that are produced by the musical instruments to perceive certain aspects from the sound. I don't believe any type of harmonic distortion from an amplifier is "desirable".