I see they don't mention Citus ( https://github.com/citusdata/citus ), which is already a fairly mature native Postgres extension. From the details given in the article, it sounds like they just reimplemented it. I wonder if they were unaware of it or disregarded it for a reason —I currently am in a similar situation as the one described in the blog, trying to shard a massive Postgres DB.
Maybe because CitusData was bought by Microsoft around the same time, so Microsoft could create “Azure Cosmos DB for Postgres Cluster”, yet another one of Microsoft’s typical product naming crapshoots.