Autoform update-pushArray doesn't work

[aparus]

I want to use Autoform type=update-pushArray. I hope I did all like in documentation and example from author :

{{#autoForm 
    collection=articles 
    class="article-form" 
    id="articleForm" 
    type="update-pushArray"
    doc=mode.doc
    scope="words"
}}

here is “words” subschema:

    words: {
        type: Array, 
        label: "Words"
    }, 
    'words.$': WordSchema,

And that is how form looks:

If I replace scope and type=update-pushArray with “update”, form looks like this:

I can’t find the answer. Please, explain it, if someone knows,