Saw this posted on Reddit by a dev and gives a good run down of the specs.
That's all quite interesting. Seems "Smart Delivery" is present here too, with a "Series S" version of the game being loaded to the console, as opposed to an overall "Xbox Series" version with 1080p, 1440p and 2160p textures. Should help with disc space. Also, if the SSD is lower speed, expanding the storage should be cheaper.