I think you misunderstood Perixoog's comment. Sudo uses PAM to ask for the password. pam_ssh_agent_auth is a PAM module that uses ssh-agent authentication instead of a password. Perixoog is saying that instead of setting NOPASSWORD, you could configure pam_ssh_agent in /etc/pam.d/sudo, and have it use the pre-existing SSH authentication as the "password", instead of having it prompt for a password.

But the part I'm concerned about is that they seem to think that having password-less sudo is a security win.