The first key to understand here is the difference between "Basic" zone and "Creative" zone. In the case of Basic zone, the camera is expecting that the photographer has little to no knowledge of photography. It takes over almost all features of the camera and adjusts based on the intent of the user (as set by the given mode).

While I don't know exactly what the basic mode does (I never use it), it most likely does things such as locking the aperture full open (to ensure the smallest depth of field and most background blur) and probably applies the Portrait profile since it specifically mentions altering skin tones (which is a processing step). The Basic modes I have seen almost always simply consist of presets that can be achieved using the "Creative modes" so while I can't guarantee it, it sounds accurate based on the little description the manual gives.

"Creative zone" on the other hand, is the "advanced" shooting mode, or as I like to call it, the non-point and shoot mode. This mode assumes that you have at least a basic understanding of photographic principles, such as metering and the exposure triangle and its elements. It allows the photographer to take control of all the features of the camera. There is often still an automatic mode in this zone where the camera will adjust for exposure based on an exposure compensation, but more features of the camera are still enabled to tweak.

In this zone, aperture is at the control of the user, as is the picture style, so a "Portrait mode" isn't possible, however setting the camera to Av (aperture priority) and locking it at wide open and setting the Portrait image processing preset should give similar color tone and depth of field to what the Portrait mode in the Basic zone did. Also note this only applies to taking JPEG images, not RAW shots (though the preview image for the RAW will be affected.) The image presets are simply adjustments for contrast, sharpness and saturation that the image processing follows when creating a JPEG from the raw image data.

Certainly the best bet to prove there aren't other changes is to setup a controlled test, with consistent lighting, consistent subject and a tripod and try both settings and see if there is a noticeable difference, however I highly doubt there will be anything seriously significant.