I’m no audio electronics expert, but I know there are wholly analog circuits that can be used as volume controls where the audio signal is not run through an exposed resistive conductor with a sweeping arm moving along the conductor.

The digital operation of the 990 volume knob or remote control could, for instance, be converted to a controllable, steady analog voltage of say zero through one volt dc and then that dc voltage used to govern an analog circuit through which the audio signal is passed when in ‘bypass’. I don’t know if that’s actually the case, but it’s possible.