Have the Virtual Copy Keyboard Shortcut apply to all selected images.

The behavior you’re observing is by Adobe’s deliberate design.

When you are in Loupe view (a single image showing), most main-menu commands operate only on the most-selected photo (the one showing in Loupe), even if you have many photos selected in the filmstrip.  Whereas invoking the command by right-clicking a thumbnail in the filmstrip operates on all the selected photos.

But in Grid view, most main-menu commands and right-clicked commands operate on all the selected photos.

Keyboard shortcuts always invoke the main-menu commands to which they are assigned. So typing the shortcut Cmd/Ctrl ‘ is the same as doing the main-menu command Photo > Create Virtual Copies.

You haven’t mentioned which OS you’re using, which is always helpful when reporting an issue that may be a bug.

Above being said, I’ve checked current behaviour on Mac and find that a virtual copy is created for each of the selected photos when using the keyboard shortcut Cmd + ’ So, it would seem that it works correctly on Mac platform.

You could try resetting the LrC Preference file to see if that helps.