We see all the time that users using a third party routine like One Drive or DropBox have trouble with not being able to re-open the Quicken data file after a Quicken Backup.
When I do an OSU, when there is a software upgrade available, you get a message on the OSU Summary window that "A new version of Quicken is available" along with the button to "View Update".
At this time, there is nothing new in the BACKUP folder of the Quicken data file location.
If you click on the "View Update" button, you are shown the release notes available at that time and a .QDF-backup file is created in the BACKUP folder.
There was no delay, no flashing of the screen to do a re-write, the backup file was created instantaneously without closing the file, so evidently, there were no pending writes to the file that were needed to be committed.
So, my question is, why does a File->Copy or Backup File (or CTRL+B) require closure of the file which triggers One Drive and DropBox to grab the file and making a backup prior to a potential software does not?