The bigger issue is that you need Google's incredible inter-DC networking, which in practice makes partitions very rare. Eric Brewer (author of CAP theorem) lays out here [0] how Spanner relies on those networking guarantees to be effectively CA.

Google's inter-dc traffic flows entirely on private links rather than on the public internet, which is very hard for any other company to match on a global scale.

[0] https://static.googleusercontent.com/media/research.google.c...