Oh, there are plenty of US satellites with classified payloads/missions; I just mean that most classified US satellites DO have orbital elements listed in the Space Force catalog.
The interesting aspects of them have to do with how far off-axis they can function. This was the major consequence of loss of the Morison leak of the KH-11 shots of a Soviet carrier to Jane's Defense Weekly — the image revealed how far off-axis it could image and some clues to how it processed imagery.