Probably not, or not necessarily, but they are some good but not perfect measurements, it's a good achievement for an individual beyond a shadow of a doubt, but I don't agree with your statement.This is the best headphone under $1000 that you can buy for 350, performancewise.
I say "probably not", because the frequency response is not particularly smooth suffering from some typical planar sharp fluctuations, albeit it's only above 5kHz where this phenomenon really kicks in, but you can still see it below that point as fine high Q fluctuations ("fine grass"). Re distortion it shows imperfect characteristics above 500kHz towards the region where we are most sensitive to distortion, albeit you'd have to listen very loud to tickle that. The ultra low distortion in the bass is good but to be honest it probably doesn't need to be that good in that area, as we are less sensitive to distortion in that frequency zone, so the ultra low distortion in that area is probably psychologically skewing people to think it's a low distortion marvel whilst "ignoring" the not so good distortion above 500Hz.
Below $350 you have very many headphones. HD600 / HD650 have better smoother frequency responses and lower distortion in the above 500Hz region, albeit more distortion in the bass......I'll admit the HD600 is not the best in the bass after EQ from my own experience, but it's beautiful in the rest of the frequency range due to it's smooth & accurate frequency response, the headphone in this review would definitely not be better from that point of view. HD560s is another one, it has low distortion in the bass and ultra low distortion above 500Hz, and it has a smoother frequency response than this reviewed headphone - as well as having very good imaging & soundstage due to angled drivers (and perhaps other different unfathomable reasons as soundstage is not fully understood albeit it's a thing). Does this headphone have angled pads or drivers, if it doesn't then chances are it doesn't have the best soundstage. To be honest a good headphone like the HE4XX or HE400i could sound as good as this reviewed headphone after EQ as they are planars that have smoother or good frequency responses that are easily EQ'd whilst having comparable (or in case of HE4XX perhaps better from some measurement sources) distortion in the above 500Hz zone whilst having worse but still good inaudible distortion levels in the bass....and also having angled pads in the case of the HE4XX which should help soundstage. My point is a blanket statement saying "This is the best headphone under $1000 that you can buy...performancewise" is a bit of a nonsense.