Seems a little disingenuous. Yes, South Carolina beat UCF in 2013 28-25, that game was a nailbiter. It seems like a major stretch to from saying "South Carolina beat the best G5 team in 2013" to then saying no G5 teams could beat any of Spurrier's better teams. I don't agree. Boise State from 2006 to 2011 was far better than UCF in 2013. Boise State dismantled UGA in 2011 and it wasn't even close. It was an extremely close game between UGA and SCar that same year, which was one of Spurrier's better years. I don't love the transitive property, but it does tell us something about the teams.
2013 UCF only lost the one game, but they had some extremely close games against mediocre teams. They beat 7-5 Penn State by 3 points and 8 of their games were within a TD. 2011 Boise blew every opponent out. 2006 Boise beat Oklahoma with 5 NFL offensive linemen and a running back named Adrian Peterson. 2009 Boise State, which might have won the title if they had been allowed to play, completely manhandled Oregon and held LeGarrette Blount to -.6 yards per rush. He was humiliated which is why he threw that punch. Spurrier's best teams were built around the running game, and while I LOVE Lattimore, he wasn't on the level of Peterson or Blount, who were both NFL superstars.
Those are some huge wins for those Boise teams. You can't rest of your hat on an extremely close game against UCF in 2013 to write off the best G5 teams of that time period.