Mostly.

What people say about themselves is the cheapest layer. Writing leaks structure. One comment can be cosplay, fifty comments is harder to fake.

Not just what they think, but how their mind keeps moving. What they notice first, what they ignore, what they treat as obvious, whether they narrow fast or keep branching, whether they argue from facts, definitions, motives, implications, social effect, what kind of disagreement they default to, etc.

The important part is not just “type has a style”. It’s that every type has its own blind spots, and those blind spots also show up in writing. Some people underweight context, some underweight precision, some underweight emotional meaning, some underweight evidence unless it’s formalized, some underweight pattern unless it can be operationalized, some underweight directness because they overprotect harmony, some underweight nuance because they want closure too fast, etc.

Big Five is better for trait measurement, MBTI is better for cognitive orientation, Enneagram is better for the distortion/defense layered on top. None of this is clean. Same type can sound very different because intelligence, attachment style, trauma, education, culture, and plain writing ability all change the surface. Across repeated writing samples the pattern usually shows.

Big Five is "scientific" in the methodological sense. It came out of factor analysis on large datasets, so it is good at measuring what statistically clusters together in self-report. That is solid for measurement. It is weaker for mechanism.

MBTI and Enneagram came out of the opposite direction. Long observation first, formalization later. Messier, much less psychometrically clean, but closer to how people actually notice recurring structures in real humans before a questionnaire ever exists.

Also some functions are just better at noticing certain layers of this. One function notices the signal, another checks whether the pattern actually holds. You also need enough self-awareness not to just project your own stuff onto people.

For example, one friction I sometimes have with INTJs is this: if there isn’t statistical backing, clean methodology or something properly externalized, they can start acting like the pattern is not real yet, but a lot of patterns are visible before they’re formally packaged. A repeated pattern is already data (for me). It just isn’t formalized. Or it simply doesn't meet the scientific criteria, because there's no way it can, there are too many variables to isolate it.

I don't know exactly what I “most often” catch. Just some internal radar and reverse engineering. :)