I read his book “Extraterrestrial: The First Sign of Intelligent Life Beyond Earth” about Oumuamua. en.wikipedia.org/wiki/ʻOumuamua it was well thought out and examines the object from many angles. He never says it was aliens. He only says that everything we know about it says it isn’t natural and could be aliens. He does say that it passed through so quickly that we really didn’t get a great look at the object and have to make some guesses about it based on observations.