I think the point is that
@amirm was extremely positive about the tonality of the Stealth and that it sounded just right. For example, he has recommended that manufacturers purchase one to have a reference for how it should sound "right".
This all sounds very attractive as a selling point (to me).
Regarding the Expanse, Amir has stated these things in a much more restrained manner (from what i took from it). For example, the review says that he found the sound better without EQ only 70% of the time, but 30% of the time it was better with EQ. This "undermines" the argument that he strongly emphasized for the Stealth: Just put it on, and you know how it's "right". The review of the Expanse reads more like a typical headphone review, with strengths and weaknesses depending on the track (not a good selling point to me, if i want to buy a headphonme for 4K).
At the same time, Amir seems to prefer the Expanse. That's hard to understand. Therefore, I would also like to see more explanations from Amir, if possible. I'm actually considering buying the Expanse. But only if it has all the advantages of the Stealth (except isolation) plus the advantages of an open headphone. If the tonality/neutrality is less "correct" and I still can't be sure, my HD800S with EQ will probably suffice(?).
Just to clarify, in case this gets lost in translation: I'm not criticizing, I'm just explaining why the questions about it are interesting (also to me).