Here are the Previews, before and after Aperture decoding. It does not seem to me that your Canon software matches the Preview from the camera, either?
The way I captured the before was to Import the RAW into an existing Project where it would not then be immediately displayed. Then I opened the Package of the Library, and then the Previews folder and copied the initial Preview prior to its being replaced by one generated by Aperture.
I fear that the problem in Apple Digital Camera RAW is that older cameras are not being well considered in updates. If I can find an older version of Aperture with an older version of Camera RAW in use, I will test.
Btw, I do not see anything like this difference in any photos I make with my Nikon D300 or D800 between the initial Preview and the next one generated by Aperture. To be clear, I am suggesting it would not impact all CR2 files from all Canon cameras -- we would have lots more reports were that the case.