I took the comment as meaning it was a requirement from the B12. I could have misunderstood what he meant though. When he said it was a B12 requirement, he may have meant that the admin or AD or Kalani's secretary or the ticket office or someone at BYU mandated that the grounds crew paint the end zones for all B12 games.
You're right though about ISU and OU. They don't have painted end zones.