The case is that we are more comfortable showing the world our extroverted functions more than introverted. So with the INTP, you will not see how analytical they really are unless you're in a close association with them. You will not see the INTJ's imagination unless the environment is appropriate. In most cases you will see the rigid Te that is particular about the way that things are done.
i agree with this, but i don't think it's about comfort, necessarily. i think that the nature of introverted functions is to deal with internal significance, and as such, it's more difficult to apply to the real world, much less share it with others. they circle inwards, not outwards; they don't naturally flow towards the external world. they speak an internal language, not an external one. whereas extraverted functions flow outwardly and tend to speak in more universal language. so it's not just that it's less comfortable to share introverted functions, it also requires using another function to redirect its flow and translate it into universal language. it takes a hell of a lot longer - it's generally impractical.
an INTJ certainly analyzes. they break down, categorize, say yes and no. it's extraverted, so it deals with the external elements of systems. and it's analytical in a literal sense, but the point is not the analysis; it's the breaking down to get to the core. both Ni and Te work to streamline and see "core" cause and effect. INTJ leads with N, so T works for N.
whereas INTPs are the ones who like to take apart mechanical things to see how they work, who play endlessly with the logic of systems, who go into full depth and know the ins and outs and find all the little errors. INTP leads with T, so N works for T. an INTP goes into further depth within the system, working at a theoretical level to assess the integrity of the system's internal logic, but we don't really get to see that. we only see the end results of their analysis, when they find errors in the system.
as for creativity, i think both are fairly creative. the INTPs i know tinker and the INTJs revolutionize ideas. INTPs are, predictably, a little more "outside the box" in their behavior. that's why i continue to like the J/P distinctions as they are. Pe expands and Pi hones, and i think J/P accurately reflects that. and INTJs are indeed more anal. hence J. they take longer to adjust to change. INTPs adjust more quickly, even though they usually complain about it.