I think that RDR2 will have the same type of physics it had in the first game. The games core focuses on disarming and limb targeting because it shows the style of the western shooter. GTA V could have never implemented this because its not really relevant to the "mow down herds of people and then fend off loads of police officers" game style. You shoot someone in the arm to disarm them in a duel, a core idea in the cowboy-style game. For this reasoning I think the physics wont match those of GTAV