But why do they need serverless Postgres for that?

They could achieve the same with normal pg, or SQLite. Or any number of other embedded DB’s. There’s also plenty of disaggregated compute options available…

I imagine they are buying the expertise in managing the transactional system rather than the IP itself. Operationally running a transactional system is a different ballgame for these OLAP players.

(of course what they're not getting is scale readiness.. it's not like these companies have anything resembling RDS level customer workloads)