I can see how that can be confusing. Some headphones have the mid-range pulled back to give more a feeling of a larger soundstage, but they don't actually have it. I'd say the E3 is pretty accurate to the soundstage. If it's wide, it's wide; if it's narrow, it's narrow. So, like I described in the review, there's less of a feeling of listening to the way the headphones impose a sound over music, and more a sense of hearing what's in the music.
One of the interesting consequences I observed with closed-backed planars, starting with the original Audeze LCD-XC, then the Ether Closed, was that it drops the mid-bass somewhat, which, as Dan mentioned, ends up with a sound more like speakers. Later on, the Harman research came along, and put forward an average FR curve that is similar to what you get with closed-backed planars.