The last line is a good indication of how sharper doesn't equate to more true to the original – think of oversharpened photographs! It sure may be more spectacular and interesting to look at, but not better to everyone's eyes.
The same goes for audio. It's clear that an excessive treble will go hand in hand with analyticalness and detail enhancement, provided that resolution is really good, otherwise it could also just sound sharp.
Yes, the Sennheiser rep in the video is trying to display the HD 800 as a «Studio» version to justify its coexistence – claiming exemplary «flatness» (= linearity) for it. Sounds good on paper. But why does Sennheiser warm the «S» version by reducing treble energy by means of a helmholtz resonator (!) just there where the often measured and critizized peak is? Note that a helmholtz resonator works as a resonance killer! So relying on marketing speach is a bit blue-eyed.
I still do like my HD 800 classic – a lot! –, but why do you think I had to develop a
modification for it? And since I have the corresponding hardware I use the built-in equalizer to further reduce the ~6 kHz peak, which (otherwise) is very audible to me.
I haven't heard the HD 800 S yet. Would like to, though. But just like the recording pros mentioned in a link in an earlier post I probably would stay with my HD 800 classic nonetheless – since I equalize anyway (that was the clue of said statement by a Sennheiser rep).