why is the ic rf shielding exposed
These look like solder pads onto which a EMI shield made of sheet metal would be soldered.


( source of picture: article Design and Shielding Techniques to Block EMR and EMI )

The manufacturer of your board have probably concluded that the board performs adequately and passes the EMI tests without the shield.  To save cost, they have omitted the actual sheet metal part.  The remaining pads don't do harm.  They are connected to ground.