No, the output of electret capsules is generally wired as a common source amplifier at Ugs ~0 V with an N-JFET. Without bias, there will be neglibible output (~essentially only the capacitive coupling from the gate to the output; if you SPDT the bias voltage to ground, you're having a >100 MOhm source impedance (the capsule) fighting a couple kOhms (bias + input resistance) through perhaps 5 pF or so.