My company does managed Postgres on AWS, Azure, Google Cloud Platform, DigitalOcean and UpCloud - https://aiven.io/postgresql. Compose offers managed Postgres (https://www.compose.com/postgresql), as does ElephantSQL (https://www.elephantsql.com/). Database Labs is one more provider (https://www.databaselabs.io/).
Google recently added beta version of Postgres to Cloud SQL as well (https://cloud.google.com/sql/docs/postgres/). Of course, AWS RDS and Heroku have been on the market for some time.
I'd claim managed Postgres market is in a pretty good shape.
Google Cloud has managed Postgres:
They announced that just a few weeks ago. And what they state on the site you linked to proves the parent's point about managed Postgres being hit or miss:
"This is a Beta release of Cloud SQL for PostgreSQL. This product might be changed in backward-incompatible ways and is not subject to any SLA or deprecation policy."
In cloud/managed space, Postgres is also hit and miss - still no good cross-region option and frankly other than AWS RDS not many other managed Postgres services.
So, MySQL rules the cloud/managed databases, and oracle/sybase/mssql rule on prem.