Earlier quoted context omitted.
If you understood how to write Go, you would write an imperative ad-hoc loop instead of composing generic functional combinators. But you have to be mature enough to jump over the shadow of your functional pride and write clean imperative code.
Loops impose order. Maps do not. Maps are in principle trivial to parallelise. That would be a nice feature.
Agree, and a map also provides an "at a glance" assurance that I'm getting a transformed array of the same size. For loops take longer to discern what they're doing just because they could be doing almost anything, including early exit.