No, with the 9-key you control what you see after cropping.
The topmost setting uses the transparency mask from the gui settings, the middle settings adds a black frame, the bottom setting uses a white frame. And this setting works immediately.
The left button shows the original size maximized and the right button shows the cropped area maximized.
When you work on a raw file the original file is not changed and the sidecar file is used on reloading to reapply the changes. If you work on a non-raw file like a jpeg, the cropping is indeed applied to the file on save and you are no longer able to revert to the original settings.