Seems like the AR doesn't ADS fully, there's a shot of it in first person perspective where it's held and an offset reminiscent of the halo series, whilst firing.
This could be a means of reminiscing over ODST's gameplay, it could be an intrinsic property of the weapon given the large, over-barrel suite (mag ammo count / compass), or (and is extremely unlikely) it or it could be that AH have expanded first person view capability.