Sorry, but the link won’t open on my iPhone, but to answer the question, I’d say they didn’t know music theory in an academic sense. I think they had a genuine curiosity about music, and grew up in a unique time period where one could hear all sorts of styles of music on the same radio station. I think they were familiar with the Tin Pan Alley era, Great American Song Book, Big Band / Jazz, blues and early rock n roll. I think through their natural talent and curiosity they developed a very intuitive musical sense. Their producer, George Martin definitely knew his music theory, so I am sure he provided some guidance along the way, but without stifling their creativity.