But my experience is that they don't really care about lower levels of college football. And for many SEC Football fans, the Big 12 is lower level college football.
For example, I have an associate at work that is a huge Georgia fan (travels across the country to attend games, etc). I was so excited to talk to him about college football in general but realized that he just didn't know much about BYU or the Big 12 or really anyone outside the top 25.
Just like many BYU fans don't consider SMU a legit ACC or P4 team, I'd guess that most SEC fans don't consider the Big 12 newcomers to be P4 teams.