I read this slightly differently, that specific machine types with Nvidia GPU hardware also have Nvidia networking for tying together those GPUs.

Google has its own TPUs and don’t really use GPUs except to sell them to end customers on cloud I think. So using Nvidia networking for Nvidia GPUs across many machines on cloud is really just a reflection of what external customers want to buy.

Disclaimer, I work at Google but have no non public info about this.