So he claims it so he is. He doesn’t hold to the Lutheran Confessions, Book of Concord. He does agree with you however in other matters, so he must be telling the truth. He is as much a Confessional Lutheran as you appear to be.
He wrote "I, a confessional Lutheran, came to the hard conclusion recently that criticisms against me not being Lutheran in much of my teaching (because I am very missional) were actually quite accurate."
If someone claims they are a Roman Catholic you just assume they are. Is it not the same for Confessional Lutherans ? Is there some level beyond confirmation they attain ? Or is it because he is a pastor and went to the wrong school, or perhaps his church is not in a particular fellowship of churches ?