> It did this not by testing me directly, but by gleaning insight into my personality based on information from my chat history.

Sounds a lot like cold reading https://en.wikipedia.org/wiki/Cold_reading

> These conclusions can feel unique and revelatory to the user

That's a very low bar. Horoscope feels unique and revelatory to lots of people.

https://en.wikipedia.org/wiki/Forer_effect

> the Barnum–Forer effect, is a common psychological phenomenon whereby individuals give high accuracy ratings to descriptions of their personality that supposedly are tailored specifically to them, yet which are in fact vague and general enough to apply to a broad range of people