Theories can be right, wrong, large or small in scope, consistent or inconsistent, incomplete, etc. Someone could indeed state that they believe reading tea leaves is a method by which knowledge is acquired. Whether you think it's bs or not doesn't mean it's not a theory. A theory is simply a explanatory description of something.
But it's not a theory. It's their hypothesis. Or postulation. Or opinion. They have to prove that they actually aquire some knowledge from reading tea leaves, and are not just making stuff up, for it to be a theory. Unless you mean colloquial "theory," which if that is the case, then we should switch to saying "the substantiated fact of collecting knowledge through science" vs "the theory of reading tea leaves." Personally I'd rather use scientific "theory" to be coonsistent.
I'm not sure why you think it's weird to that's the scientific method as a theory of knowledge because that's essentially what it is. It's the idea that one can learn about reality through empirical study.
It's weird, because learning through science is an action, not a phenomenon. One that has immediate results. Results that have been done and confirmed over and over millions of times. And most importantly, because "the scientific method is the theory of knowledge" to me sounds like saying "a painting a sheet of paper red is the theory of applying red paint to paper." It's not so much a
theory as it's just what it actually is.