They have a standard setup everywhere, with the same Python version, and the same libs available.

So basically, for them, Python requires no fiddling and works as is.

Same for the shell. They say "use [[]]" because they know that compat is not a problem: it's the same bash everywhere.

Google has millions of servers, billions of lines of code and surely of lot of experience with deployment, managing complexity and handling teams.

I'm kinda trusting them on this choice.