That probably refers to file locking, which prevents other apps from changing a file after the first app has opened it. I wouldn’t expect Obsidian to set a lock on the file, but maybe it is somehow? This probably isn’t a pressing issue and might be Linux-distro–specific, but if you’re up for it I’d like to try to figure out what’s happening.
I know you worked around the problem, I was just hoping to find out if Obsidian is doing something wrong so the root of the problem can potentially be eliminated. You generally want to keep the setting you changed at its original setting.
I just tested with LibreOffice on Mac and don’t see the same problem, and the locking setting is set to “true”, so if Obsidian is doing something wrong it’s platform-specific.