The link describes something very common. The only difference I can see is that they ask you the email to figure if you are coming from yahoo or Google while t

The link describes something very common. The only difference I can see is that they ask you the email to figure if you are coming from yahoo or Google while the most common pattern is to show two buttons. I don't think asking your email is a good idea, email is a something they should ask to the identity provider instead.