Focal length is an intrinsic property of the lens, it has nothing to do with the size of the image circle or of the sensor behind the lens. I think you may be under the mistaken impression that for EF-S lenses, Canon somehow alters the focal length numbers to compensate for the fact that they are used on a crop sensor - that is not the case. 55mm on an EF lens is the same as 55mm on an EF-S lens - both would give identical framing on an APS-C camera, and both would give a wider angle of view, but identical framing on a FF camera (if the EF-S Lens could be mounted on one, that is).