My guess would be (given the size of that array) that this is done to prevent rate limits rather than cost. It could be that this was advised by Google themselves because they could not provision the correct rate limits due to end of year. It's hard to imagine a client of this size isn't in direct contact with Google Cloud engineers. Pretty sure they're paying for it too. Also, this may have been done just for the open source commit of the project to prevent leaking token? Can't jump to conclusions here.

Google does the same thing in Google Pay Indian version. Government mandated that no one app can have more than 25% transaction volume of the country for UPI. So Google partnered with 4 banks, essentially having 4 UPI apps in the eyes of government.