I've since looked at one of the Cabrio's up close; the opening at the bottom of the one I examined was every bit as gynormous as Alan's. I sent an email to their CS, the jist of which was if the Book model had the same butchered opening, they could cancel my order as well. No reason I can fathom to cut a slot that big and continue it up the back of the case.
There could be a case for misleading advertising. Their homepage shows the cabrio with no such cut out at the back. In my opinion, while it does allow easy docking, the cut out is just too bad and defeats the "premium" feel of the case. After a week of useage, I fee like the sides are "widening" and there is a feeling that the phone could pop out of the case (it hasn't happened yet).