Interest concept, going to consider if this is something I want to use in future work.

One suggestion to simplify your final example, instead of:

function makeShoppingCart({ 
   addProduct,
   empty,
   getProducts,
   removeProduct,
   ...others
}) {
  return Object.freeze({
    addProduct,
    empty,
    getProducts,
    removeProduct,
    someOtherMethod,
    ...others
  )}
  function someOtherMethod () {
    // code 
  }
}

You could simply do:

function makeShoppingCart(productList) {
  return Object.freeze({
    someOtherMethod,
    ...productList
  )}
  function someOtherMethod () {
    // code 
  }
}

Since all fields are just past directly into Object.freeze().

Cheers!