The title of this doesn't properly match the contents. This is basically a how to set up an enterprise SSH environment using certificates. This doesn't tell you anything about "How to SSH Properly".
I'm considering doing a future post on how to set up U2F for SSH with hardware devices (like a Yubikey) as well. I'm curious if you have anything else you'd like to see on this topic.
So maybe the title shouldn't be "I like ssh certs" but "ssh security for organisations", but your point still stands.
It's the name of the TOTP PAM module they use, which was created by Google: https://github.com/google/google-authenticator-libpam
That's not a coincidence, of course. It's purely sales and marketing. To be clear, the ultimate goal of this blog post is simply to get you or your employer to give them some of your money -- that's it.
(To be clear, giving an external entity full control over authentication and authorization of your critical servers is definitely not doing "SSH properly", IMO!)