The only difference between the FA and SA carrier is that the FA carrier has a ramped lip which engages the trip lever of the FA pack. The semi pack has no trip lever so the ramped lip on the carrier never makes contact with anything at all. Nor does it matter.
The reverse combination is not functional though. If you have a SA carrier with a FA pack, the part of the carrier that would engage the trip lever is machined out so it never pushes the trip lever now. As such, the sear catch doesn't get pushed forward to release the hammer. So the hammer can not fire the gun.