I think the whole "introverted extravert" thing has been a bit exaggerated. It probably stems from some distorted notions of extraverted behavior. Like extraversion might be associated with Se, Te and Fe, so in comparison, Ne seems different. (Hence, yes; ISP's might seem to be the "extraverted introverts).
Ne dominants are all Get Things Going in Interaction Style, and the outward focus does generally draw them to approach people, like other dominant extraverted functions do. It also makes them "informative", and having a "light and airyness" about them on the positive side of their personality. These are the classic "extroverted" and "Sanguine" traits.
It's true that some may have focused a bit too much on "outgoing and gregarious" as definitions of extraversion, but that doesn't mean that there isn't some truth to those descriptions, and that they should be totally discarded. Any type can act withdrawn at times for whatever reason, but Ne dominants do seem to be usually outgoing, at least in their own ways.