You are correct, Ehrman is not a mythicist and believes that Jesus existed as a person but argues that the gospel accounts of his life are based on myth. He is an agnostic atheist so doesnât believe in God, let alone that Jesus was God. The historicity he questions is the accounts in the gospels and the majority of the New Testament.
It begs the question though, what difference does it make? If you donât believe the gospels are true but are based on myth, what difference does it make that a Jesus existed or not, or whether he was one Jewish preacher that was crucified by the Romans or perhaps an amalgamation of various Jewish preachers who were crucified by the Romans. The evidence suggest he may have existed but the accounts in the gospels were made up long after his death, based on earlier myths.
Ehrman has admitted that you cannot teach Religious Studies at a major university in the US and deny that Jesus existed as a person, which is interesting.
An agnostic atheist is someone who doesnât believe in God, but doesnât claim to know whether God exists or not. A gnostic or positive atheist claims to know God does not exist.
The latter position seems to me as irrational as a fundamentalist religious position.