https://cloud.google.com/custom-machine-types/
Quizlet's post alludes to Google's attitude as well. With exception of GPU instances, Google's VMs are generic. You are able to get incredibly fast SSDs, best in class networking, etc, on just typical instances. Benefits are pricing is simpler, spot instance/preemptible VM market is simpler, and you get much more architectural flexibility.
(Disclaimer - work on Big Data @ Google Cloud)