Except that is a false dichotomy. This isn't about inlining 'pure' functions (I know your example is IO, but they aren't mutating your program's state), it is about avoiding functions that are only used once and/or that mutate state.

I've used the same technique - instead of creating a function that might be awkward due to all the inputs and outputs, I'll create an inner scope {} with nothing around it. Only the variables that it modifies/initializes are left on the outside. This is a simple way to enforce more of a data flow style within a function and ends up being a useful organizational tool. It is also similar to 'let' in some languages.