The idea to me is pretty simple: just do the same as with Jungian typology. The centers "heart" "head" and "gut" aren't unlike functions such as feeling, thinking, etc. So it's not too odd to find that one has a reaction from each category.
Some argue that you can explain all the types appearing in your psychology besides the core one using lines of integration/disintegration and wings. However, I've found this commits the same mistake as saying someone with Ni "has" Se -- actually that's a pretty vague statement, and the use of "having" in "having Ni" for a dominant/aux Ni is pretty different from the use of "having" for Se -- in one case it colors the unconscious, and in the other case it orients the ego. Having something in the unconscious is in a way like just setting up an opposite for your ego to go against, so you only really have this function in the sense that you define your ego based on the tension it has with the unconscious.
Similarly, lines of integration/disintegration don't represent ordinary strategies so much as they help define what your main type is all about based on a sort of complementary nature.
So the analogues of an auxiliary/tertiary are really closer to the tritype types. Wings are again things that I think implicitly define your core type -- you can basically think of 5's withholding as an interface between 6's doubt and 4's sense of isolation. That is, the head anxiety of 5 results from this doubt combined with a sense of estrangement, and one constantly refines the search for how to approach the world.
