I definitely agree it's underexplained in type safe.ai's materials.
I have to assume it's a reference to the fast, heuristic, intuitive "system 1" process in humans, as opposed to the slow, procedural, reasoning "system 2".
This theory is recognized, among others, in Daniel Kahneman 2002 Nobel prize on Economics.
I think that this specific part is not super interesting if your harness just recovers from invalid LLM outputs.
The latency and cost - yes, those are super interesting.