Wrong, RNAV with VNAV.
Uh, don't know if you know someone who has Jepps but chart 12-2 dated 2 MAR 12 is the RNAV (GPS) RWY 18 at BHM, presumably this is the chart the UPS crew was using. I doubt they would be using the LOC RWY 18 but I will concede that it is possible and legal. And, if they did do the LOC approach, they would normally have vertical path guidance from the FMS.
I refuse to view aviation through the prism of "big iron" only.
I'm not trying to be pedantic, I realize you perhaps don't fly large aircraft for a living.
The only aircraft smaller than the A300 that UPS operates is the B-757 so I guess in that sense you could call it a light twin. But somehow I don't think they would be doing a dive and drive in a widebody in 2013.