I'm pretty sure this only works if you use images with Google's sauce added, which means your instances run Google daemons that do things like network, user, and ssh config.
https://cloud.google.com/compute/docs/oslogin/#how_os_login_...
...But if you use an image with Google's sauce, there are Google daemons running on it, just not for this.
https://cloud.google.com/compute/docs/images/install-guest-e...