I also noticed that voice guidance continues even when I turn it off on my D2. Lowering the volume shuts it up, but it still mutes the audio for guide voice instructions. If I remember correctly, there *is* another setting that will cause it to not mute A/V audio, but makes it more of a pain in the @$$ - especially if the second setting is one that requires the parking brake to be set.
I like to use navigation on certain trips just to keep up with my ETA and I don't need or want guidance.
I imagine Pioneer knows about the issue, and am sure they care. And I'm not surprised to find them unresponsive to a user pointing out the problem. Sadly it's typical for big companies like that.
Oh well...