At first glance it looks as if the 952 is now equipped with a grip safety, for the back-strap is movable, where the 52's is not.
But it isn't a grip safety, it's a firing pin safety that depends on the grip rather than some connection with the trigger. This is a descendent of the 1930s Swartz firing pin safety once found on Colt Government Models and now seen on Kimber's Series II pistols, or S&W's latest 945. It is a better design and has no harmful effect on the trigger pull, which is a creep-free 4 pounds.