I've been round and round about the t-shirt fan thing so there's no reason to go through it again. Those who use it are just using it as a very poor trolling attempt.
Major conference NCAA football is a business, just like the NFL, NBA and MLB...with the University heads playing the role of owners. In Texas, people who are NBA fans will chose the Rockets, Spurs or Mavericks...NFL fans will choose the Texans or the Cowboys...MLB fans will chose the Astros or Rangers...and NCAA football fans will choose the Aggies or the Longhorns. There is a separate dynamic with alumni angle, but overall it runs because it's a business that depends on the casual fan for success...just like pro sports.
So if one was to make a distinction about fans, it would be just like any other sport...loyal fans and bandwagon fans...which seems to be the same angle you are taking.