> 3. Better type errors. With currying, writing (f 1 2) instead of (f 1 2 3) silently produces a partial application. The compiler happily infers a function type like :s -> :t and moves on. The real error only surfaces later, when that unexpected function value finally clashes with an incompatible type, often far from the actual mistake. With fixed arity, a missing argument is caught right where it happens.

'Putting things' (multi-argument function calls, in this case) 'in-band doesn't make them go away, but it does successfully hide them from your tooling', part 422.