What is the 'breadcrumb' label in Google Webmaster for webpages markup

Question

Recently, I've noticed a 'breadcrumb' label show up in the Structure Markup section of Webmaster. Nothing shows up under that label for any of my breadcrumbs:

They do show up for that page under the BreadcrumbList section:

And breadcrumbs are activated in search results:

---

So, what is the 'breadcrumb' label looking for?

This is the markup that's used on the page for the breadcrumbs:

{
    "@context": "http://schema.org",
    "@type": "WebPage",
    "url": "https://www.j-26.com/seo/essentials/webpages/",
    "breadcrumb": {
        "@type": "BreadcrumbList",
        "itemListElement": [
            {
                "@type": "ListItem",
                "position": 1,
                "item": {
                    "@id": "https://www.j-26.com/seo/",
                    "name": "SEO"
                }
            },
            {
                "@type": "ListItem",
                "position": 2,
                "item": {
                    "@id": "https://www.j-26.com/seo/essentials/",
                    "name": "Essentials"
                }
            },
            {
                "@type": "ListItem",
                "position": 3,
                "item": {
                    "@id": "https://www.j-26.com/seo/essentials/webpages/",
                    "name": "Webpages"
                }
            }
        ]
    }
}