Brown repeats this "literary device" in interviews, on his web page, etc., and refers readers to non-fiction works which purport to substantiate these historical facts which he really doesn't believe, but just acts like he believes, all the time.
I guess it's all ok, and we are silly for responding, since he really doesn't believe it all (though he never says he doesn't believe it all), and what he really believes (against all evidence) is what really counts.
Thanks for educating us in the nuance of authorial practice. I will ever after judge all writers by what they really believe, which I will make up out of thin air in spite of what they say. I am so much smarter now.
You're welcome. All you have to do is remember what a novel is -- and is not.