All the time Ctrl+0 worked as expected: Fitting the image left a several pixel margin around the image so the selection and other tools could be clicked slightly outside the image.
Now, since vesrion 23.3 the Ctrl+0 is changed: the image fits without leaving the small margin. Without the margin it is impossible to start the selection exactly from the corner of the image, etc.
The margin around the image should be restored in an upcoming version. Initially it was introduced for usability purposes.