Per the order guide found here:
http://fiestafaction.com/forums/2011...der-guide.html
Fiesta S has steel mini spare (page 2)
Fiesta SE sedan with SFE package has aluminum mini spare (page 5)
I suspect the sedan needed the Al spare to get in the same test weight class as the hatch with the steel spare. Since the sedan is called out specifically, I suspect the SFE hatch has a steel mini spare. The Al will cost more so they'll put it in as few cars as possible. Potential weight save for lotus-phile hatch owners who still want to have the security of carrying a spare
Also notice AL spare for sedan with powershift in the sport package. Probably for same reason.