In the booklet it says that the recording was made, edited and mastered in DSD. I thought most discs were edited in PCM and then converted back. Interesting. Also, HDTracks has it as 24-88.2 rather than 176.4, which seems a bit mean. Great disc!
This may have to do with the A/D converter build in the microphone itself. Those are currently mainly 88.2 as far as I know. I see the same specification for recordings made by Polyhymnia International. They also record on 88.2, with Neumann and Schoeps microphones. Maybe leaving out the analog mic. amplifier provides for a better overall result than with analog amps. PCM converts easily onto DSD anyway (from 2 x 44.1 to 64 x 44.1). The main benefit of DSD is its superior D/A conversion at the end of the chain anyway. ....