It is very hard to type people sometimes, and there's just no easy way of getting around this.
Depending on how well someone is functioning in life can have an enormous impact on which cognitive functions we see manifest in their behavior. And even if someone IS very well-functioning, this does not preclude the possibility of one having developed lesser functions in the past out of necessity. And so they can demonstrate skills which are more traditionally associated with other types, yet still maintain a dominant orientation to life as determined by their core. Experiences play a large role in the rise and fall tide of one's mental functions, as we experience life and puzzle things out in that ever-changing tide of internal "data". That data is of course input from every function (not simply "Te," eg).
It is important to realize that the functions manifest in various levels - or shall we say, depths. Just because you observe something "Si" is not the whole story. This can lead to wrong conclusions. Since the functions are entangled within this "metabolic" model (having a "center of cognitive mass" - so to speak :wink - timing is everything. For example, one may be more apt to experience Si for a very brief interval until receiving input from other more dominant functions "knocking on the door," wishing to contribute to the "data discussion." Expressing an Si theme in a moment, even intensely, is not the same as expressing it in a more fundamental way over a long period of time.
Sorry, this is probably all terribly obvious, but I just felt like ranting. (ISO truth).