Sure but there are plenty of OLAP solutions like Greenplum, and extension-based offerings like Citus and Timescale, that can all partition and scale across node

Sure but there are plenty of OLAP solutions like Greenplum, and extension-based offerings like Citus and Timescale, that can all partition and scale across nodes to massive datasets with column-oriented storage. AWS Redshift is also built on Postgres (although a much older and customized version).