I think that's partly because people don't understand what extraverted vs. introverted mean in the MBTI sense. It's not about sociability. It's actually about how much external stimuli someone likes more generally. This might be social stimuli (Fe), but it could also be physical stimuli (Se) (for example, liking being physically active or out in nature) or more conceptual stimuli / external ideas (Ne), etc. Or a computing analogy: what's your ratio of IO to CPU time.
Also, at least in the cognitive function interpretation (which IMO is the only sensible theory in the jungian/mbti family), introversion and extraversion do not apply directly to persons. They apply to thinking processes. An extraverted person is then just a person who uses an extraverted thinking mode more often than not (everyone is theorised to use both extraverted and introverted thinking modes). As you note this bias can be more or less extreme.
Indeed, it's been observed that it can both be influenced by external factors (e.g. social expectations), and that it tends to become less extreme over time. As such, a persons "type" is generally considered to be determined by what their preference was in childhood, and (the type) is taken to define their baseline personality (cf. genotype) from which their actually observable personality (cf phenotype) develops.
It would make sense that the E/I axis would be clearer if early childhood experiences were used. That would make me a clear extrovert. I think the questions should be updated for that context or at least have some additional framing around the test.
This idea was surprising to me too, but when I thought about it I realised it shouldn't be:
- We know that different people frequently react differently to the same stimuli (and that this is true even of very young children).
- Basically everything else in the human body shows genetic variation. It would be weird if the brain didn't.
- There is a strong evolutionary rationale for a population having a variety of complimentary congnitive styles.
I think the MBTI is most interesting is it taken to be only the genetic component of personality (providing us with AFAIK the only theory of the structure of that aspect of personality), while simultaneously leaning into the idea that personality is modified by nurture and environment (but that these changes are not described by one's MBTI type).
Could you possibly expand on the details of "generated an personality embedding from data"?
The MBTI is just a projection of the personality space like the more accepted Big 5. From my experience data-mining behavioral data at scale it’s a pretty good mapping and the relative value questions are adequate and the 4 dimensions do explain a lot of behavior to the point that it is very useful - a fact probability contributing to its success. My main gripe with it is the extrovert - introvert axis is a bit weak with many people being close to the middle. I’m more extroverted around intelligent people which doesn’t happen as often as I’d like, a trait held by far more commonly by ENTJ/INTJ than random chance.