If you take the grips off you will see a piece of shiny sheet metal running vertically up the "spine" of the frame. Besides acting as a guide to run the magazine home, it is also a leaf spring which, when bent or arched slightly, applies friction to the rear of the magazine, acting as a brake. In fact, it is called a magazine brake. Yours is probably straight and applies no pressure to the magazine. My PCR compact is made this way as well.
The descriptions of both models on the CZ website are silent on whether or not mags are supposed to drop free.