He didn't seem arrogant to me from the Lex podcasts. He seems to have no problem admitting when he doesn't know something or when he was wrong. Maybe his overuse of the "I" pronoun gives the wrong impression?
More the overuse of his name to name other things and the fact he has been talking about revolutioning science for at least 2 facades without doing it.
I think it depends what you mean by arrogant. To me, naming things after yourself is a bit of vanity. But I also see the advantage of building a brand with a consistent meaning. You may not believe everything Wolfram has to say, but I think that the naming here conveys a clear meaning to users.