From https://chaos-lang.org/docs/11_decision_making > Decision making(a.k.a. control structures) in Chaos language is only achievable on function returns for the sake of zero cyclomatic complexity. ... > At first glance, defining the control structures in this way might seem so unnecessary or inconvenient but this is the pinnacle of writing 100% testable, clean and error-free code in any programming langauge by far.…
I mean yes it's either obviously wrong or hyperbole, I assume the second. But I think the idea is that by forcing each branch in a case to be an separate function they are forced to be unit testable.
Edit: If code needs certain number of conditions, they will be there in this or that form, that cannot be avoided. I would like to see real benefits of their choice in real non-trivial examples.