I think they did it because they originally intended the hunting rifle to be able to be converted into a pistol. Their default pistol grip animation places the left hand OVER the right hand. To cycle a round using on a right handed bolt action pistol, the player would have to remove their left hand, switch the pistol from their right to left hand, chamber with the right hand, move the gun from the left to right hand, then place their left hand back over the right hand. By making the rifle left-handed but held in the right hand, they could use the same animation for cycling a round from a pistol grip or rifle grip. It looks like s***, but it saves on creating another animation.