That's part of the reason I won't take a hard stance on this one. But from everything I've been taught, pickups that respond to acoustic occurrences, are usually doing so because the coil has microphonic qualities, as you mentioned. But a tightly wound, well potted pickup should not. Sometimes you hear some reverb from trem springs or the strings if you shout or make a noise into the pickups, but an epoxy potted active pickup, for example should be less prone to it, as well as an efficiently wound, well potted passive one. Two different pickup manufacturers have corroborated that all things equal, the pickup does not understand how it is mounted. That is to say, it doesn't alter the signal. Theoretically, if the pickup were mounted so loosely that the magnetic disruption could physicaly move or vibrate the pickup sympathetically, there would be a difference. But that would require a suspension mounting like those on condenser mics. The pickup vibrating, in and of itself, would create no sound.