Headphones.com sells shitty enthusiast grade headphones and IEMs to people in the hobby. Therefore, their target is actually a preference tolerance. Basically, they lowered their standards to accommodate a wider range of badly tuned audio gear so that they can sell a larger variety of products and not piss off manufacturers or people who want to give away their money for bad products.
Here we can see their tolerance in a review of the Focal Azurys compared to another headphone. As we can see, the tolerance accommodates both headphones fairly well with little to no deviation outside of the preference bounds. A headphone can look like a ravaged chainsaw went to town on it from 20Hz to 20kHz and still fit within their tolerance. Truly pathetic but what would you expect from a headphone store? I'm also pretty sure diffuse field isn't even their baseline so it's tilted or something. I'm too lazy to care what they're doing over there. Either way it's sad.
