The launch post makes the borrowing explicit, contrasting “fast, intuitive System 1 thinking and slow, deliberate System 2 reasoning” and placing the new model class on the fast side: quick typed decisions that software consumes, with no written reasoning attached.
Kahneman’s subject was people. System 1 in the book describes human cognition, its speed and its characteristic biases, and makes no claim about how any machine is built. Using the name for a class of models is an analogy about the job being done, not evidence about architecture. What Jev does internally is unpublished.
The analogy does carry one useful implication. In the book, System 1 produces an impression and System 2 either endorses it or overrides it. That maps onto how TypeSafe says to build: the model returns a probability, your code applies the threshold, and low-confidence cases go to a human or to a slower model. TypeSafe puts the boundary plainly as “Your code encodes the risk tolerance.”
Note the spelling difference when searching. Kahneman writes “System 1” and “System 2” with digits, while TypeSafe writes “System One”. See what is a System One model and the system-two model entry.