Benjamin is nervous around new people so he needs to take greetings slow. As part of his training, he receives praise when he does something as simple as sniffing someone's hand. For most dogs this is pretty routine behavior, but for Benjamin it's a huge step as it shows he's being brave.
For any dog with an anxiety issue, it's best to have people bend down to pet him/her. If your dog turns away from the person, this means it's too much for them right now and you should end the greeting.
Great job Benjamin!