Jeremy Waszak notified me of this change on Twitter yesterday and I confirmed, it indeed does submit any page, not just your own, to the Google index. This is in addition to using the Fetch as Google to submit your pages, you can use this tool to submit any page to the Google Index.
Here is what it looks like:
After you submit it, it says "page added to indexing queue," "submitting a page multiple times will not change its position or priority."
Of course, this does not mean the page will show up in search - but it does place it in the queue to be indexed.
This feature was not in this tool back in May 2016.
Forum discussion at Twitter.