How carefully worded! It implements a "core subset" of data types and "key parts" of the SQL dialect. It does not sound like they've made it trivial to just silently swap your RDBMS with Spanner. Still, it's come a long way from the days when Spanner did not even have SQL DML.

Thank you, this should be the main link.

Looks like the docs are live alongside the announcement –

"The PostgreSQL language in Cloud Spanner": https://cloud.google.com/spanner/docs/postgresql/overview

"PostgreSQL interface" under the Concepts section: https://cloud.google.com/spanner/docs/postgresql-interface