A family of Microsoft spreadsheet software with tools for analyzing, charting, and communicating data.
I figured it out!
Click the Upcoming Features button near the right end of the title bar (the little horn icon) and turn off the "new experience" switch near the bottom of the Coming Soon pane. Restart Excel and Poof! The annoying autosave feature is gone.
Hope this helps!
Since it is related:
I also figure out that you can move the quick access toolbar to be part of the title bar so it looks like Excel 2016 (and so you can still have a "save as" button on the top left corner after you remove the autosave stuff):
Click the little arrow down button after the quick access icons and the last item is "show above the ribbon" - that moves your quick access icons to the title bar like in Excel 2016, which removes one of those huge new bezels MS added in Office 365.