Canon Europe explains the ins and outs of in-camera lens corrections:

Once you enable Distortion Correction, the edges of the image may be cropped slightly. However, the angle of view that is listed in a lens’s specifications and MTF chart is always based on the digitally corrected image. This means there’s no need to worry that you’re losing several degrees of the viewing angle from the uncorrected image, as this is taken into account in the lens design.

I always wondered if the corrections reduce the size of the image compared to the advertised focal length. The answer is that Canon delivers the full size they claim in their marketing.

I am ok with this. In the days of film, digital lens corrections were not available. Digital lens corrections make smaller and lighter lenses possible while still getting an excellent image.