I installed mine as a full recirc as well. A blank off port plate is included with the BOV.
As Bliz stated, once the volume of air is measured by the Mass Air Flow Sensor in the intake, the ECU adjusts for the proper fuel mixture. If you dump off some of that air using a BOV, now you have a momentary lean condition which can cause backfires, etc...
If the same BOV is configured for full recirc as a BPV, you don't have that issue since all the air has been accounted for in the fuel trims, as it passes thru the engine.
Also, due to the location and orientation of the BPV on the 5th Gen LGT, if you were to run this BOV as a 50/50, the open port would be facing upward, exposing the slide piston to the elements ... (i.e., maintenance issues).
Since a 50/50 BOV setup does not provide any performance gains, it's a matter of how badly you want to hear the air vent, and willingness to deal with the associated problems that come with it.
Here's some good info related to the use of BOV's and BPV's: