indeed, the most sense being made regarding the AFX tracks on FDTS is that they're simply original pieces integrated into the record. "The Beauty of Being Numb" in particular seems to be a bizarre amalgamation of different works assembled afterward — perhaps they were looking to find a followup to the fairly short backmasked "Mr. Self Destruct" section and decided the AFX track made an interesting companion (but also that it needed the mouthpiece sounds from "Eraser" to make it feel right — Richard James' attitude about the whole thing convinces me he didn't originally include those sounds himself).