Some interesting news:
According to this tread, the OP of which contains an internal document that explains how the ASD module operates,
ASD may be automatically disabled if any of the speakers are disconnected.
Because of the popularity of disconnecting the center channel speaker on 2 Series models with any stereo to improve the soundstage, this means that ASD is permanently shut down when that speaker is disconnected.
What disconnecting the speaker doesn't do is take the ASD module out of the signal path, which means that the operational noise that the module emits is not eliminated. The TechnicPnP harness is still the only way to eliminate this.