Microsoft blog: “The new iCloud for Windows app introduces a new iCloud Drive experience for Windows 10 users powered by the same Windows technology that also powers OneDrive’s Files On-Demand feature, enabling users to be more productive offline on mobile devices and quickly share files on iOS.”
The parent poster should've made it more clear!
Because the Apple Support link posted does not mention this collaboration anywhere, unlike the Microsoft blog.
Edit: I'm trying the "updated" app now. No changes appear to have been made. It is still slow and buggy as hell, it still installs a ported and outdated version of half of the frameworks of OS X, as expected.
Collaboration has been heavily implied in all articles I've read about this. That Microsoft made a blog post[1] about it, saying "Apple and Microsoft", must mean something.