Why does document.addEventListener('load', handler) not work?

I’m trying

document.addEventListener('load', handler)

in Chrome 46 and Firefox 42, and it’s not working. I can get it to work if I try it on window, as in

window.addEventListener('load', handler)

The MDN documentation for the “load” event says

Target: Document, Element

So why doesn’t it work on the document? Do the docs need to be updated?

The spec states that it is fired at window and at certain (special) elements like <img>:

Fired at the Window when the document has finished loading; fired at an element containing a resource (e.g. img, embed) when its resource has finished loading

Source: https://html.spec.whatwg.org/multipage/indices.html#events-2

Is window.addEventListener('load', handler) the proper way to do things when the document is ready (DOM loaded, but images, etc still need to load)?

Use DOMContentLoaded event of the document object.