it is true. ENFPs (and to an even greater extent, INFPs). have a bit of a "switch" factor between several layers of their personality.
with ENFPs, our primary psychological state is a creative, fun loving and curious individual who is eager to learn and collaborate with people. this side is often frivilous and enjoys ridiculous forms of dress and having the "shock factor" with people.
Fi in and of itself has at least 2 very different layers to it
1) calm, fantasy oriented, sweet, great with animals and children, extremely relaxed. this is the way most INFPs (and many ENFPs) are most of the time.
2) however, if provoked or fighting for one's values, an NFP will completely switch directions, turning from calm and sweet into an intense, passionate and heroic figure who will stop at NOTHING to deliver justice to the wicked. it is in this state, especially when under pressure, that I believe NFP are among the most dangerous types.
if Te is developed, it lends to a more formal, business oriented side that offer more rational, conscious decision making and better organization (before I developed Te organization was pretty much impossible for me, even now I really don't like it). this side is also quite polite and hospitable and lends to good hosting skills when combined with Ne and Fi. I often use this side of my personality around older people because they are often otherwise condescending and treat me like a child.
my best friend is ENTP (we thought he was ESTP for the longest time because he spent years developing Se doing hip hop dancing), but now that we know that he's ENTP, it makes a lot more sense because an ESTP could not keep up with my crazy ideas =P
for the most part, we're a lot alike. both of us are ridiculous, fun loving, spontaneous and brimming with ideas. the main difference I see is that his introverted side is more cold and calculating and he is better with details (although he insists that this is learned and that it is so boring that it hurts). until recently, he never really excepted the full extent his personality has changed dramatically once he started to except the full potential of his strengths. this is perhaps due to his upbringing. he was abused and as such had to develope rather unnatural precision in order to avoid being hurt. for this reason we first thought he was ENTJ, then INTJ, then ESTP and now ENTP, but this one makes the most sense out of all of them so far. at the end of the day though, we're much more alike than different.