OLAP databases need to be able to handle billions of rows per hour/day.

I super love PG but PG is too far away from that.

Reading between the lines, given they're talking > 1 million rows per minute, I'd guess on the order of trillions of rows rather than billions (assuming they retain data for more than a couple of weeks)

PG can handle billions of rows for certain use cases, but not easily. Generally you can make things work but you definitely start entering "heroic effort" territory.