Why is this wrapper function created?

Playground:

@module("./math.js")
external sum: (int, int) => int = "sum"

let result = sum(3, 4)

import * as MathJs from "./math.js";

function sum(prim0, prim1) {
  return MathJs.sum(prim0, prim1);
}

let result = MathJs.sum(3, 4);

export {
  sum,
  result,
}

I’m a little confused why this wrapper sum function is generated?
Am I missing something syntax wise?