Javascript: recreating Array.from?

Question

I came across this code for stripping Marketo forms of their included stylesheets. Let's assume that the code author is a super senior engineer. Array.from() could have been used instead of defining arrayFrom (functionally at any rate), so why use the latter?

For my part I'm trying to understand the arrayFrom definition (first line of the codeblock):

1. bind() sets this to the provided value, here [].slice (why?)
2. call() allows us to call getSelection with the this value bound by bind.
3. getSelection() returns a Selection object (or string in Firefox) of the selected text. This I'm unsure about. In its use, arrayFrom gets passed an array (or NodeList) of stylesheets and returns an array of the same stylesheets (a shallow copy thereof?) no differently than if Array.from were used, so the functional bit of bind and call must be to alter the this value in a desirable way. Not sure how that acts on [].slice though.

Anyone? I'm clearly missing something.

const arrayFrom = getSelection.call.bind([].slice);

// remove element styles from <form> and children
const styledEls = arrayFrom(formEl.querySelectorAll("[style]")).concat(
formEl
);

styledEls.forEach(function (el) {
     el.removeAttribute("style");
});

     
// create an array of all stylesheets in document
const styleSheets = arrayFrom(document.styleSheets);

// loop through stylesheets and check for ownerNode properties on each
styleSheets.forEach(function (ss) {
    if (
    //array of <link/> elements tied to stylesheets
    [mktoForms2BaseStyle, mktoForms2ThemeStyle].indexOf(ss.ownerNode) !=
      -1 ||
    formEl.contains(ss.ownerNode)
    ) {
      ss.disabled = true;
      } 
});