I've now read Kenneth Grahame's original version of The Reluctant Dragon and learned that the parallel bathing to introduce the dragon and the knight was totally the invention of the Disney story department, as was the dragon playing the flute.
Furthermore, the knight in the original is St. George. Perhaps the Hays office, the movies' self-censorship body which was closely alligned with the Catholic Church's Legion of Decency, objected to a cartoonified St. George. Or perhaps Disney made the change before they could object.
In any case, St. George in the book is not a poet either, so Disney's story department was not shy about reshaping the material to make a stronger film. They invented enough visual business so that the animators always had something to work with. While the film is fairly dialogue heavy, it doesn't feel that way because the characters are always doing something when they talk. That's a lesson we seem to have forgotten over the years.