== "Authentication" is bad title == 

 Mutual Authentication is not Authentication. After SMP, you cannot verify you are talking to the person you think you are. You can just be sure there is no third party in between. For example, Alice and Bob have a conversation. Cary wants to use man in the middle. After SMP, Alice and Bob can be sure no one is in the middle relaying the message. But Cary can still attack Alice and do a SMP with Alice alone, and pretend to be Bob, without relaying the message.