It's currently not integrated with any 3rd party systems. I'm guessing either those apps have to do something to integrate with Files they're not doing today or Apple simply haven't done that integration yet.
Sharepoint storage today is currently integrated with iOS via OneDrive for Business, Microsoft Teams, and Sharepoint apps. The first two I use regularly and work well, the latter I haven't used as we have other systems for intranet and sharing type activities.
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I expect Microsoft will do a good, perhaps even great, job integrating with the new functionality in iOS11. In my opinion the Office apps and others around it are the best productivity apps on iPad, and to a lesser extent iPhone, by quite some margin. Windows, for me, no thanks but I thoroughly appreciate the fact that I can open Office on the web, iOS, Android, Windows and Mac and have a very similar experience across them all.
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