It is definitely boat-tailed.
I was thinking of starting a new thread on this and probably should have. Split it off?
I've always seen this style of spoiler NOT boat-tailed. The Fusion is the first one I've noticed with that feature.
Also I've noticed sometimes the "end plates" are flush with the sides of the car and sometimes they are set in.
Set in from sides and boat-tailed
Flush with sides and no boat-tailing.
Set in from sides and no boat-tailing