Scrap the scare quotes, it is obviously false. Less code in the small does imply less code in the large. It doesn't need any justification, it is a tautology: if it takes less code to write all the small things in your program, the program itself will have less code overall.
Or did I misunderstood the meaning of "less code"?
>What about programming in the large?
less code -> less code at large -> win
>What about efficiency of naive implementations?
like a stack overflow version of it the starters always come up with in Java? what exactly are you talking about?
>What about maintainability?
What does FP or any of this thread for that matter do with maintainability? You can write unmaintainable code in any language.
These are a very limited subset of what really matters in software engineering. (I would also remove the naive implementation part.)