It's more like what CockroachDB or TiDB use underneath. They all are suited for local clusters, but cannot perform well enough replicating across multiple far away datacenters over public internet, latency trade offs would be unbearable. Spanner is a bit different, with Google's fancy clocks and fancy networks, it can get better latency trade offs that might satisfy more applications.

Citus I can't remember, but if Citus does it properly wrt consistency, it should be in the same category as CockroachDB and TiDB, there is no magic.