This is reasonable. But do you feel this must always be measurable? The general consensus is that lower distortion is always better, but is it really? We respond differently to harmonics. Lower, even order are more pleasant that higher, and odd order. Disconsonance is not always pleasant to the ear, we like natural progressions. An example of this unnatural sound is the Lydian mode.
Oh I absolutely accept that some people may/do prefer a bit of added harmonic distortion, amongst other non-linearities. I have read that even harmonics are less dissonant than odd but JA in Stereophile states that 3rd harmonic are pleasant too. Don't know myself.
I think there is a whole mass of audio enthusiasts today, maybe even the majority of kit enthusiasts, who praise the sound of equipment which produces extra distortion. Several reviewers always prefer distorting products to clean ones. Also I think a lot of expensive "high end" kit has a tailored response, on purpose or by accident, so it sounds different and then many people will equate much more expensive and sounding different with "better".
I have no proof of this just the observation that kit with high distortion and frequency response modifying levels of output impedance (in power amps) are always praised by certain of them.
I have no problem with people enjoying inaccurate playback, I enjoy my record players after all, my problem is when the people are convinced that it is not the inaccuracy they are enjoying but some magic fairy dust which can not be measured which makes it sound more real. That is simply completely cockeyed IMO.
Paying silly money for it is even more barmy.