"Class D" doesn't mean a component is bad, it means it should provide satisfying sound but isn't near the state-of-the-art. The Stereophile review said that the sound from the analog outputs was a couple of notches below state-of-the-art (the TAS review was kinder), so I assume that this is what determined its rating, along perhaps with the 96 kHz sampling rate limitation.
Too bad, not the rating I mean, but the DAC, since I've been considering getting one as a temporary sound source . . .