Correct me if I'm wrong, but I think it depends on if the rear hatch was unlocked or not before you started the car.
If you click the hatch button and the door unlock button before you enter the car the hatch will be unlocked before you arm the car.
If you entered the car using only the door unlock button on the remote, the hatch will be locked.
I'm pretty sure that's how it works on my '09.
If you click the hatch button and the door unlock button before you enter the car the hatch will be unlocked before you arm the car.
If you entered the car using only the door unlock button on the remote, the hatch will be locked.
I'm pretty sure that's how it works on my '09.