Thanks for the whitewash pic, Brentil. I've been meaning to do something like that - it's what I've been trying to say all along.
The "hump" is the fuel tank, with the vent, sender, etc on top. It's obviously a mid or bottom fill (not impossible - only requires filler neck about 25-40mm above the top of the tank, looks like that's pretty close from my last trip to NAIAS, today) and a very simple box shape. It's not complicated and ahead of the trunk like the C6, or the Z4 or other roadsters because form-fit tanks are 2X - 3X as expensive as a simple plastic box-tank.
I guess this packaging inefficiency is just the price you pay for a record-time "new platform" with no styling sacrifice. Look at how close the darn thing is to the original car back in 2002, and you can see what I mean. I don't think you could get closer without going way above $25,000, or living with inefficient packaging decisions (like the reverse swing decklid, or top stowing in the trunk).
Remember, this platform only got the go ahead about 20 months ago or so.