Okay, so it's bothering me - comparing the fusion to the jetta....
So I grabbed an image, made a quick rough model, and threw it through the solver....
Red= 55mph or higher
Blue = 0mph
From this, I'd say the truck deck can be useful as flow near the vehicle on the rear end hasn't lost much velocity. Just a guess
I'm still curious as to why that slide (earlier picture) doesn't attribute the extended deck lid to any gains.... Perhaps it just does a great job at straightening the flow, to avoid nasty lift conditions at 200mph
