Thanks for pointing out that request. It is similar but not the same. I've added a comment there. The difference is that the other request is for the users to be able to click a save while I'm asking for the form to automatically save partial responses to the server. Similar requests, but not identical. I think this is worthy of being tracked as a separate enhancement request in the product backlog.
I would like to know if partial responses are now collected even if an user doesn't reach the last page.
Data is only collected after the user click on the "Submit" button or "Proceed to Checkout".