That is odd. I guess it's really being a purist design, but hardly practical. First HP amp I've heard that does it this way.
I disagree, but to each their own. One man's "neutral" is another man's "boring" is another man's "bright" and on and on. I'm out of the neutral game. I'm into enjoyment. I love the Abyss for what it does better than any other headphone -- resolution, speed, clarity, soundstaging, bass. You can get all of those with a capable amplifier, some more or less than others depending on the amp. What I'm not crazy about is that for me, it can get a little hot on top and a little thin through the middle. But that can be mitigated with a complementary amp. Right now I am using a tube amp, best I've heard so far, but always curious of other options and open minded to different sounds.