TourDeForce
Hard-core CEG'er
I have the same oval-shaped pass-through for the fold-down rear seats in my Maxima. There's got to be some engineering reason why they didn't increase the size of it, but personally it makes the thing almost useless for bulky items.
Based on the shape, I'm guessing the floor side has some bracing bracketry to stiffen the chassis from twisting. It is, after all, a fairly large car. Fully loaded going into some of the parking lots & driveways I've seen on this site, it'll need that help to keep its shape.
I drove an '07 (I think it was) and I thought the car was rather substantial, yet had handling that surprised me. The model I drove had the CVT. Weird... but VERY smooth. I wonder why they dropped it. Was it having problems?