and even if we did how do you map the test results to a subjective listening experience?
Thats super easy, if any distortion/non-linearity/errors/etc. are below established audibility tresholds, then it’ll be transparent. THD+N of -130dB vs -140dB is not meaningful for usage as they are both below the noise floor of any room, even though it’s easy to say the latter is better. A DAC that has a frequency response of +/-0.1dB is better than +/-0.2dB, but they’ll sound similar and be audibly better than one that’s +/-1dB. IMD that’s 60dB below the fundamental will be inaudible with music (may be audible for test tones).
Indeed, getting concrete values for what’s transparent is difficult, but if the values are far better than any human tests have shown, than that’s good.