Message is incorrect when "Save As To File" is used to rename read-only VTF file.
You can see correct message like following when you try to overwrite the read-only VTF file.
But, when you try to save with new name, the message is "Saved successfully.". Saved VTF file doesn't have any update. It was just copied from original VTF file, and the VTF file is also read-only. It means modification will be lost despite of you use "Save As To File", when you update read-only VTF file.