sources??
the review you linked above clearly describes less warmth and smoothness in the ie300, and people, esp less experienced, often confuse smoothness and warmth for less 'detail'/'openess'/'air', which may explain all the other conclusions in that comparison.
The ie 300, while clear, was not smooth to me, partially due to poor tuning, but I have also found some of that boominess or rather a weird quality to the bass regardless of tips, as they describe above. The ie 300 mids were really good, but nearly impossible to appreciate because of tuning.
So far I have more hope for ie 200 than ie 300, even if it is somehow technically inferior to ie 300, which is really not possible to quantify due to variations in hearing and preferences , the tuning is a step in the right direction for me.
I bought the ie 300 based on a bunch of similar positive impressions, they turned out to be quite different to how they were described (some ways good, some ways bad) e.g " dark yet balanced" this is like the opposite of ie 300, they are fairly u- shaped, neither dark nor balanced, but you can figure this much from an FR graph.
I think I might be lucky one in that iem FR graphs so far have reflected pretty closely what I hear.