That’s just cultural literacy. Capricorn One references a seminal 1978 movie about a faked Mars mission and subsequent cover up. It became fodder for not only other fictional imitations but whack jobs everywhere.
The author of this article isn’t responsible for his readers understanding of his pop-culture references. It’s sufficient that he made them.
I know what Capricorn One referred to. A book about the theory need not necessarily advocate the theory.