They got it entirely wrong. Peterson has explicitly and repeatedly stated that he never intended to target young men specifically but, since YouTube's audience is predominantly male, supply-and-demand decided the distribution for him.
Edit: the article actually uses the vague term "the implied readers"... which I guess means it's the author's own implication. I have to agree with the above, heavily-downvoted comment above as such baseless speculation appears to serve the writer's agenda over the need to inform the reader.