In this case, i suppose i'd specifically mean the 'listening' tests, or as loads for measurements.
Personally when i look for reviews, i look for people who use similar gear - my own decision to get the udac2 was based off this review and another one i can't remember the location of, which had someone using the udac2 with the same headphones i use.
I'm not talking about covering all the bases. I'm talking about measurements with another typical range of headphone impedances, and suggested one that's fairly common - in short, adding another datapoint to better reflect diversity.
At the moment, you've proven
1) 1/2 the testers can't tell the difference - with no idea if the bias is their source
2) the udac2 sounds horrible with low impedance phones - with no data on a typical medium or high impedance phone
3) it sounds worse than something that costs 10 times as much, and is a lot bigger.