There is no doubt this audio-Gd unit inserts an extra 20-30dB of harmonic and intermodulation “special effects”, compared to better measuring units.
I call them special effects, because at these low levels around -70dB they interact with headphone or loudspeaker drive units, which on their own also have their distortion spectrum around those levels.
I think the language and tone we use can be a little combative. Distortion on a scope or visual measurement may look “frightening” but audibly it is not always perceived as “distortion”. It is perceived as the character of the complete system.
Remember these DACs don’t connect directly to the cochlear nerve in our ear. They connect to a preamp, amp, headphone or speaker driver, then through air and finally our pinnae/ear/cranium and torso. All which affect the perceived sound.
Do you want evidence?
Exhibit A: A 11” woofer with 4V applied (2W into 8 ohms)
Reference: Hificompass.com
https://hificompass.com/en/speakers/measurements/accuton/accuton-s280-6-283n
If you think that looks bad, it’s all relative.
It’s actually state of the art, one of the best 11” woofers available, as far as electrodynamic speakers are concerned.
Here’s a “frightening distortion spectrum” of a 5.5” midwoofer:
Reference: Hificompass
https://hificompass.com/en/speakers/measurements/scan-speak/scanspeak-15w8530k00
This little driver is the famous Scan-Speak Revelator, considered by many as one of the best 5.5” midwoofers available. And in fact mild variants are used commercial speakers, like a certain US$10K bookshelf speaker, made by manufacturer Wilson A, or W. Audio.
What’s my point?
I’m not defending this audio-Gd unit, or apologising for it.
But I’m also not calling people who like it as tone-deaf, audiophools or idiots.
At -70 to -80dB THD down, these units definitely impart their own character or special effects into your signal chain. Whether you like it, or not, is personal preference.
I prefer the other DAC, from the other Chinese manufacturer. The one with the SINAD of 120dB.