The bullets exit from the muzzle of the gun then makes a 45 degree bend to aim at the center of the cross hair, instead of coming straight out of the muzzle of the gun. This allows the player to quickly raise the weapon and shoot at targets without the gun being pointed at the target. The bullets should always exit straight out of the muzzle of the gun in a realistic manner, with an exception to how previous Arma games zero their guns. Having the muzzle of the gun being where the bullets are directed, will mitigate the problem of having too much of an advantage when using a cross hair, and will maximize the fairness, realism and immersion of a gunfight.
The new method of allowing the bullets to bend towards the middle of the screen allows players to shoot around corners if you free look pointing the tip of the gun out of the corner. The new system will also be problematic for people who use Track IR or VR headsets for head movement the problem being that there is never a center of the screen for those users. Track IR is allowed in Arma 2 and Arma 3 and should stay that way. Track IR was also allowed in the early stages of Dayz Standalone.