@scottbb You can mod anything t o fit anything. There's an extra tab on the lens flange ring that is the difference between EF and EF-S flange rings. It can be machined off. I guess one could also take a flange ring from and EF-S body and attach it to a FF body (precise alignment might be difficult, though, if the screw hole patterns are not the same and new holes would need to be drilled with a mere few µm of tolerance...) so that EF-S lenses could be attached.
For what it's worth, the first Canon APS-C camera, the 10D, does not accept EF-S lenses, either. None existed at the time it was introduced. It has a straight EF flange ring with no extra cutout to allow the extra tab on EF-S lenses to mate with it.
