There are two ways you can read that statement. The question is, what did he mean by "that news"? Did he mean the existence of Art. I, §13, or did he mean the fact that the court had never issued an opinion interpreting it?"Did you know that the Constitution of Virginia has a companion to the Second Amendment? It’s Art. I, §13, and believe it or not, the court has never, in all its history, issued an opinion interpreting it. I was surprised when I read that news in today's opinion,"
If the former, then you are right that he is totally unfit to serve on the Virginia Supreme Court. However, if it's the latter, then it's not as unreasonable. In the absence of any other evidence about him indicating that he is unfamiliar with the Virginia Constitution, I would be more inclined to give him the benefit of the doubt, and assume that he meant that he was surprised the Court had never interpreted Art. I, §13 before.