I think “Update modified timestamp on export” and “Generate the following naming fields on export” are swapped.
If “Update modified timestamp on export” is unchecked and “Generate the following naming fields on export” is checked, the exported font will have a timestamp, but the custom version string will be invalid.
If “Update modified timestamp on export” is checked and “Generate the following naming fields on export” is unchecked, the exported font will not have a timestamp, but the custom version string will be valid.
Sorry, my description is wrong. Checking or not checking “Update modified timestamp on export” does not affect the version number when previewing the font.
However, if “Update modified timestamp on export” is checked, the version information column will be forced to add the timestamp and software version number when previewing the font.
If it is not checked, the version number information is customized.