What is “bottom-less” storage? This just seems like a managed hosting of PostgreSQL, nothing else…
We wrote a custom storage layer for postgres, so in our setup, postgres node (k8s pod actually) doesn't store any data, and it is easy to start/stop/reschedule it. So while we actually are DBaaS, the closest analogy here is Aurora or Alloy, not RDS-like setups.
A bit more details are on https://github.com/neondatabase/neon