And this is where the situation seems to be different for Mac.
If you look very carefully at the screenshot of Finder in my initial post, you will see that the file names are from JNA_0020.NEF to JNA_0024.NEF, as are the .dop file names.
But, if you look at the names on the thumbnails, you will see that the names are: JNA_0304.NEF, JNA_0305.NEF, JNA_0311.NEF, JNA_0316.NEF, JNA_0023.NEF and JNA_0319.NEF. That despite the names that Finder shows.
You will notice that the virtual copy of JNA_0023.NEF is correctly (re)named to match the physical file name. This is because I had deleted the database and restarted PhotoLab after creating the virtual copy; so, obviously, PL is reading the name from the physical file for the virtual copy but it is reading it from the internal .dop name for the master. If I don’t do a database deletion after creating a virtual copy, PL continues to show the old file name on all thumbnails, despite the physical files having been renamed.
I am certainly not advocating any change that would affect the Windows version if it doesn’t exhibit this fault; I just want the Mac version to behave properly.
[update]
I just repeated my test with PL4.1.1 and the problem still exists.
I copied the same small folder of files I used for the first test to a test location and renamed the files to ensure that the physical file names matched those in their .dop files, just as if they had not been externally renamed.
I then opened PL4.1.1 and, sure enough, everything appeared fine with the thumbnails showing the correct physical file names.
Then I closed PL4.1.1 and used Finder to rename the image files and their .dops.
Upon reopening PL4.1.1, the thumbnails for the virtual copies were correctly renamed but those for the master copies were still showing the original file name.
Notice that the thumbnail shows a different name on the virtual copies (the new name) to that on the master.
Since they are both derived from the same physical file, I have to declare this a bug that needs fixing for the Mac version.
If you create a virtual copy from a misnamed master, the thumbnail will show the name of the copy as the same as the master, even after closing and reopening PL4.1.1. It takes deleting the database to reveal the difference in names between the master and its virtual copies.
[update 2]
Just to prove what can be done if you edit the file name in the .dop file
@StevenL this seems to be totally reproducible. Can you look into it?