By converting it to PCM just as you and I said ;-)I'm saying that is not the case. It's always PCM going into the multi-bit modulator.
Besides, you haven't told us how DSD async resampling works?
Simple DSD-inflation data in that case, mapping 1 to some positive high value and 0 to the same value but negative. The final DAC is PCM so nothing else can be feed to it. Obviously.
But we're nitpicking here. The key takeaway is that the DSD modulation causes no or very little signal-correlated RF glitch energy and this is why DSD mode has lower distortion.