Not a CZ52 owner, but I would assume it lowers the trigger pull by eliminating the firing pin block safety.
If other words...it's not the firing pin itself that is causing the lighter trigger pull, but the modified (eliminated, actually) firing pin block mechanism--you no longer has such a stiff spring to over-ride in order for the firing pin to travel forward.
In other words...you get the benefit of a lighter trigger pull, at the expense of one safety feature.