You gotta look at the function interaction when it comes to this stuff rather than impressions based on stereotypes associated with the personality profiles. That way it has more explanatory potential, or at the very least is more interesting as a subject.
'Introverted' and 'extraverted' in Jungian typology doesn't refer to those terms in the conventional sense but rather to functions
, e.g. introverted v. extraverted feeling, introverted v. extraverted thinking, etc. In a nutshell, introverted functions relate to the subject, while extraverted functions relate to objects. We all have introverted and extraverted functions in different preference order.
To take an example at hand: thinking preferences as exhibited (IMO) between Twilight and AJ. Twilight as an INTP would be a lead introverted thinker, so her thinking is going to be deductive, cataloging, basically working toward a system that makes sense to her
; AJ (as an ISTJ) has auxiliary extraverted thinking, which means her logic is more "out in the room", lateral, and more oriented toward actually doing things in the real world.
The call between ESTJ and ISTJ was made based on personal experience. ESTJ's are supreme in-the-moment problem solvers but are much less oriented toward long-term stability like the ISTJ is. Conversely, they tend to have a more flexible disposition whereas the ISTJ can be impossibly stubborn. ESTJs also tend to have the attitude of "it's easier to ask forgiveness than permission" about them which, while it personally drives me bonkers irl, is an undeniable and cute part of Applebloom's character.