Pure speculation on my part but perhaps the glass rear window pivots through 90 deg like a clam shell, the flaps in the targa roll hoop open out and the targa top pivots through 180 deg like the flip top on the Ferrari Superamerica then the rear window closes back down over it. It would mean the targa roof covered the rear seats as a sort of inverted parcel shelf (unless they've found an ingenious way to fold it up as it pivots backwards).

Here is a simple sketch of what I mean minus the required pivot arms.

Mechanism.JPG