Originally designed that way, yes, but in the past few years I think the design technology and growing portable listening audiophile crowd has forced companies to make more audiophile type CIEM's with huge soundstages or hyper trebles sort of going away from the dedicated stage monitor sound (like UM3X) and getting these things to sound more and more like headphones.
Well I quite disagree with the last few posts. A delicate rendering of treble is one of the keys to "audiophile" (if we must use this term). Even Etymotic acknowledges that most will prefer the ER4S or ER4P to the ER4B. The ER4S is generally considered the "audiophile" choice. The ER4B is more accurate in its treble and simply too bright.
Speaking of which, if flat frequency response equals "audiophile", why not just get the ER4S (or ER4B)? They won't sound as good as the ES5 but you will save a bunch of cash and they will be more "audiophile" by that definition.
Lastly the ES5 is very much a hybrid monitoring/consumer offering. Westone used to distinguish the two by providing a mid hump for stage monitoring. That ended with the ES5. I am also quite certain that the majority of their sales are consumer. They have a successful product - a good one too.
I do think that the positioning of the ES5 as a consumer oriented product vs. a professional monitoring solution is a semantic issue. It's consumer in the sense that the general public has access to it, but that only comprises a very small subset of the population. The entry barrier is simply too large when you consider cost and the time/effort/resale depreciation/blind trust associated with purchasing a product unheard (Westone doesn't offer demo units for the ES5 that I know of) that also requires a trip to the audiologist. Heck, had the TG!334 been available in the states for $900, I would have just gone with that as there's less involved in getting it into my hands, and similarly, I'd think most audiophiles would sooner opt for the Westone 4 as opposed to the ES5. It's designed for stage monitoring first and foremost I think, as that community would by and large be the main target demographic for the ES5. The fact that it's good enough for audiophiles is a fringe benefit for Westone that can be advertised with a couple of words on their website.