Regarding: https://social.technet.microsoft.com/Forums/office/en-US/4a15e472-a265-4058-b439-7d79c2670817/xls-file-will-not-open-in-excel-2016-only-gray-view
I'd like to be able to reply to that thread, but "Reply" just bounces me back to the top of the page, with no indication as to why it's not working.
Anyway, regarding this quote:
We are also investigating a more permanent solution that allows our users to remain secure as well as minimize disruption to existing user experience. We’ll provide updates on this in the coming days. Thank you for your patience.
How do we track progress on the permanent solution? This has disrupted my site's user experience. Generating full-fledged Excel documents takes a lot more coding/resources to accomplish than the lightning-fast HTML as XLS solution. We're in the process of undoing the optimization (we changed from native file generation to the wrapped solution because of performance issues, and now we must change back) so our users can see their generated files without asking them to go through extra steps on their end.