Carbon fiber saddle have been available for over twenty years now. Almost all of them flex. They are not significantly different from a 1958 Unica Nitor #55 made from nylon. Except that they are lighter. Basically all nylon shell saddles go back to the Unica Nitor whether or not padding has been added.
Why would an unpadded saddle automatically be uncomfortable? Leather saddles are unpadded. Leather saddles have been with us since there were bicycles. If no padding saddles did not work bicycles would have died before they were born.