BBDs analog or digital ground

[Dimitree]

While watching the schematic of the EHX Deluxe Memory Man I noticed that they used two different ground points, one for the LFO and clock generation, and one for the audio signal path. Those two grounds are then joined near the voltage regulator negative pin. This arrangement is present in any analog/digital design l, so I'm familiar with this. What puzzles me is that the BBD ground pins is shown connected to the "digital"/"noisy" ground only.
In other analog/digital designs I've seen, where ADC and/or DAC chips were used, those chips had two pairs of supply pins, one for "digital" and one for "analog". That also meant that when laying out the PCB, you could easily split the ground plane underneath the chip so that the analog and digital sections are separated until they reach the supply voltage regulator.
How does that translate to the BBDs? Ideally you would put the digital ground plane underneath the BBD, or no ground plane at all, and connect the ground pin using a track?
Thanks and sorry if the questions sounds dumb

[ElectricDruid]

I would guess that if the clock generation uses the "digital ground", then they have no choice and have to use the same ground for the BBD.

There's no way you could have separate power and grounds for analogue/digital sides on a BBD, because it's all one thing. In that respect, mixed signal design techniques don't translate to BBD at all. It's an interesting case since it's not a digital system, although it is sampled.