Rtings came down on the 820 a bit based on the frequency curve - but do they understand the psychoacoustics of sound? Do they really know what curve is best?
https://www.rtings.com/headphones/tools/compare/sennheiser-hd-820-vs-bose-quietcomfort-35-ii/669/565
Pretty interesting ratings. I have quite many headphones from their list and there is some correlation between what I hear and what they rate.
However, indeed those ratings seem to have too technical focus, even for their "Critical listening" category. For instance the Bose QC-35ii gets very high ratings but it doesn't sound very refined or natural to me. The HD820 and a lot of other Sennheisers got worse rating but sound better to me than the QC-35ii (not that it's bad, no, it's good for what it has been designed for, i.e. listening to music on airplane, bus, train, car, street, office - though for office there are better ones).
To state the obvious, take the input and some grains of salt, but let personal listening in your own context be the deciding factor.
Anyway, based on my experience, problems in measurements sooner or later will also appear in subjective listening observations. Any bigger dip or peak in the FR or CSD or impulse anomaly will be heard and talked about, especially when a new model will fix them. Good measurements are the minimum requirement. If that is achieved, subjective listening is the next step. A few headphones out there can pull it off. I hope there will be more and more of them.