I became interested in personality theory a few years ago, when my wife got her license to administer a Christian temperament analysis, and she tested me and several friends and family. I came to see how the theory helps us understand ourselveds and others. Then, one of these friends encourages us to take the Keirsey Temperament Sorter online. We both come out as ENFJ, which while possible for here, was way off for me. I then set out to understand the 16types system, and compare it to ours. Ours is based on FIRO and uses the ancient four temperaments of Galen (Sanguine, Melancholy Choleric, Phlegmatic), but has concluded that there was a fifth temperament, as well as the three areas (From FIRO) in which temperament can be blended (social, leadership and deep personal). I happen to fall into the new temperament in two of the areas, while being Choleric in the leadership area.
I had become so enthusiastic about this, that I looked for somewhere to discuss it. Unfortunately, I ended up on largely NF boards which were not into theorizing on this stuff. (And it took a long while before they could even speak up and communicate this). One had a resident expert who could break down all the 8 archetypes of Beebe and all, but no one could wrap their mind around the apparently foreign FIRO scales. But I had come to see a very likely parallel, particularly in the Keriseyan temperament and Berens Interaction Styles model. Also, Enneagram is similar, with its so/sp/sx variants, and it seems a lot of people want to integrate Enneagram with MBTI.
With this correlation, I had expected my temperament mix to correspond to INTP, and it did seem to fit me a lot. But then others said I was too enthusiastic, and displayed too much Fi and Te, so that I was more like ENFP. Learning more on the functions from Berens' and others' books, I can see it is more likely, and that type did fit to some exent as well. I am just not as socially outgoing, inspiring, entrancing, etc. as the ENFP seems to be described. Yet I'm too enthusiastic to be an INFP. So it seems it may be the fifth temperament, which expresses as an introvert, yet "responds" as an extrovert, yet does not really fit in the four temperament systems, that is being picked up as both extraverted, and its overdriven "Feeling" preference overshadowing the Choleric influence, which would be more pragmatic and structure-focused. (i.e.NT'ish, though Keirsey correlated them differently)
So that is another possible explanation. The type expert I mentioned had said she ran across a "boatload of ENFP's" who considered themselves introverts.
The explanation given about Ne being different from the other extraverted functions was an interesting likelyhood too.
All of this stuff is fascinating, and each model has its own unique perspective to offer. I'm really inspired by Linda Berens who also integrates several models.