Interesting comment, I have a question, not just about those particular IEM, in this thread, all IEM in general. If I understand your post, you are saying that insertion depth will affect the frequency we hear, much more than the IEM actual FR, if this is the case, is it just not easy for every one to insert those IEM, just so they sound great to them.
As I was new to using IEM to listen seriously, at the beginning I was having a little trouble to get the Zero to sound really great all the time, now with practice, it is not an issue anymore, but it tells me that, indeed, how they sit in your ears, can be a deal breaker and is much more determinant in the quality of your experience than many understand, if only having been exposed to headphones.