Yeah when you attach a grip to your camera you can turn it to portrait orientation without having to have one hand up over the top of the camera. I went to a local camera store the other day and tried one out - it was funny because with the grip on and the camera on portrait orientation, it felt SO much like it does in landscape that when I brought the camera up to my eye I found myself bringing it to where the eyepiece would normally be instead of where it actually was, and confused myself momentarily.
It seems like a really nice addition (and after trying it I really want one), but from a technical standpoint with everything else being equal, you'll get the same photos with the grip as without. The comfort level may help you hold the camera steadier, but otherwise I don't see why someone would mention it among the EXIF settings. Personally I'm saving up for another flash before I get the grip.