Well, noise shaping without dither is the way that Sony was doing “super bit mapping” many many years ago, and you don’t hear about that anymore. Because noise shaping without dithering is basically defective or at least very ineffective. It has guaranteed noise modulation, almost by definition because as you say, with no signal there’s silence.
The whole idea of “auto black” is much ado about nothing (pardon the pun). I never use it. It’s not needed and only people with eyes and meters are concerned about dither noise, which you can’t hear at 16 through 24 bit levels anyway.