I had the privilege of reviewing the GS2000e very early on, as part of a tour that Todd the Vinyl Junkie (TTVJ) arranged. In exchange for posting a review, tour members were allowed to try the GS2000e for a week, then send it to the next person on the tour.
My review is part of a long thread of these tour reviewers and is located here:
https://www.head-fi.org/threads/grado-gs2000e-loaner-program.809914/page-13#post-13061167
The review compared the GS2000e to the Grado PS1000, GS1000i, GH1, RS2e, Sennheiser HD800, and HiFiMAN HE1000. I also compared the GS2000e being driven by a variety of amps.
The comparisons were made with the GS2000e against two other headphones from the list above, on each of 10 acoustic characteristics, with a 1st place-2nd place-3rd place ranking being given on each of the 10 features, assigning 3 points to each first place, 2 points to second, and 1 to third. A total score for each three way comparison is at the bottom of each chart... high score wins.
The GS2000e had overall higher score than the PS1000e, GS1000e, GH1 w/ G cushion, and RS2e. It had a lower overall score than the PS1000. Its score was comparable to that of the HD800, HE1000, and GS1000i (differences of fewer than 3 points overall are considered insignificant.)
Several months after posting the review, I purchased my own pair of GS2000e's, which continue to delight me, not only for their great sound, but for their light weight, comfort, and great looks. I would never consider the response of the GS2000e (or any other Grado except the HP1000) as flat, which is what the reviewer in the video stated.