Tested on c.nc.com
I noticed this multiple times. I have a shread md file. Someone edits it on the desktop and sync it back. If i try to open the document later I get this:

with the option to either use the current version or use the saved version.
Also a hard refresh of the browser and re-open the document doesn't help. Maybe some server-side caching? I would expect that I always get the latest version from the storage. The only place where such a comparison makes sense to me is if you have a sync conflict because people edit the file at the same time in the browser and on the desktop. But that's probably also hard to detect...