bandai zmogui padet, o jis nesamones sneka
    The A4/B6 aerial works off the rear screen which actually comprises multiple (four) aerials via an aerial switch box an amplifier, this aerial system is called "Diversity".
    The idea is that the aerial with the strongest signal is utilised at all times.
    The black iso-aerial connector actually carries the RF signal to the headunit. The small brown/pink connector is used to feed power to the aerial amplifier switch box - if this cable is not connected then the aerial switch box/amplifier has no power and will pass through the default aerial signal with no amplification resulting in poor FM reception.
    I believe the above linked adaptor you indicate will pass the necessary power to the rear window aerial amplifier system resulting in optimum Radio reception.