It's neither. It's something else new we're trialling. It's very difficult to tell with the camera transition, but just as the view hits first person, the player is retracting the stock on the weapon (as it has a retractable stock), which is something you can now choose to do. That "half aim" is essentially "ironsights" when you don't have a stock out on a weapon, so you don't hit yourself in the face from the recoil.
There are pros and cons to having the stock in. You'd only want to do it when you're expecting to be in close quarters and the sights would be restrictive or there are walls/objects that would force your weapon lowered if it was at full length.