One thing that puzzles me is what the plan was if the third row was not selected (though I imagine there are other cars with optional 3rd rows that have this same issue).
Unlike the Model S, the seats don't stow below the existing framework (drive tunnel), they stow on top of the drive tunnel and that height is taken into account in creating the flat cargo floor. I'm guessing that some optional 3rd rows in other cars may have a similar fold and tumble and "stow below the flat cargo floor" system, but I'm not familiar with them.
With the folding 3rd row the hatch opening lines up with the rear tray which lines up with the backs of the folded seats and everything is flat with no lift-over for loading items.
If that row is simply deleted then we have a stair-stepped storage area with the tray even with the hatch opening, dropping to the top of the rear drive tunnel where the 3rd row would have been mounted, then dropping again to the floor of the vehicle. There is also the likelihood that the missing seats would leave a gap at the far end of the tray with nothing to close it off or attach it to.
Or, would the tray have been lowered to be even with the top of the drive tunnel creating a lift-over to get things in the trunk?
Or, would the tray have been deleted leaving a really deep floor with a hump over the drive tunnel (and a bigger lift-over)?
Or, the tray could be extended to where the 3rd row would have ended and squared off creating a flat cargo floor and a not-quite-flat (due to drive tunnel) under-floor storage area.
Or, ...?