I'll just point a couple of issues with this review as a longtime fan of these cans.
First off, the harman target curve is being treated as an objective standard and deviations from it are measured and shown as deviations from a flat response. The harman target is not representative of a flat response. Furthermore, when the beyer trio got in production there was no such thing as a harman target to aim for obviously.
Nevertheless, you can easily eq these headphones to match the harman target. Same way you can eq any other headphone to match the harman target if that's your preference. Stock frequency response has stopped being of any interest these days for most applications. EQ is easy and free. Whatever your own preference curve might be, nobody's stopping you from adjusting any headphone to it.
Regarding power requirements. These headphones, as specified by beyer can handle a max of 100mW. The measured sensitivity of 704mv = 97db/V means these headphones are good up to a max of 111dB at 5Vrms for the 250ohm regions. Pushing past 5Vrms to do the 114dB tests is out of specs and distortion will obviously be extreme. The power requirement of 100mW@250R is rather steep for your average smartphone, but nothing any modern headphone amp would worry about.
The impedance hump up to +100ohms in the bass region is fairly common among headphones. A quick look at the venerable hd650's review by amir shows the nominal 300ohm impedance rising up to 483ohms in the bass region. Just the way it is.
THD at 94/104 is harder to justify. It's definitely not as bad as it looks on paper. To me it's either inaudible or simply doesn't bother me in the mix, considering it affects mainly the sub 100hz region. Others might be more sensitive. Julian Krause posted a
THD test a while back that can give you an idea of your real tolerances. Again, looking at the results the hd650 got in the same test, while clearly better, it's nowhere near great either. Something to keep in mind (plus that they cost 2-3x as much).
Bottom line here is that their shortcomings are well known. The FR is what it is and if you don't like it, you can simply eq it. And you absolutely need an amp to drive them, especially if you want to eq them. New knowledge out of this review is the bass THD. Subjectively it's a non issue and pretty much every headphone suffers from it in some degree.
Bearing in mind the price (around 120e in Europe) there's still not much competition for these cans, as far as over head open backs go. The build quality is unmatched even by headphones costing 5x as much and the comfort is top notch. I've had some sets for almost 2 decades and they still look and sound pristine. Seen people with sets that go back over 30 years and are also in supreme condition. This is a headphone build to last.
Considering that after eq they all sound more or less the same and real world performance does not seem to suffer in the slightest by the arguably poor bass THD, the value is still there. Until somebody comes up with a quality build that measures better and costs about as much, these ain't going anywhere.