In science one tries to tell people, in such a way as to be understood by everyone, something that no one ever knew before. But in poetry, it's the exact opposite.
With a slightly different emphasis this doesn't need to be seen as such an insult to poetry. Maybe poetry shows something known in a new light, or perhaps connects the known to the unknown, mysterious.
From the small amount I know about Dirac, I would think he might admit to the value of this sense of poetry in physics, the connecting of something small, well-delineated and clear, to a larger, richer, more amorphous body of material. He's been refered to as a magician, and perhaps this is a key to that magic.