Does Devialet Decimate DSD?

[Confused]

I do not have much DSD format music. However, I do have some experience of feeding a Devialet DSD. This was during a demonstration of a D800 being fed by a dCS Vivaldi upsampler. The source material was mostly redbook, but I listened to a set of tracks twice, once with the Vivaldi upsampling to DSD, the second time upsampling to PCM. The thing is that it definitely sounded better with the dCS rig outputting DSD. This is not what I expected, the Devialet ADH architecture is inherently PCM, so if you feed a Devialet DSD, the first thing it does is convert to PCM via MAT, it shouldn't sound better but somehow it does. The point is, if the DSD MAT conversion was anything other than very good indeed, the D800 would not have sounded best when fed DSD. I have to conclude that the MAT DSD conversion works superbly.