I saw Burns/Cook in the pub. Surely it's obvious that Cook's back gave out, but Burns was trying to claim that it was some sort of wonder-punch. As for the fight being sanctioned, I don't think it's a problem. The mandatory fights (in theory) are when they face the organisations's top challengers. Outside of that, they're free to make whatever fights they want... whether it's a big money fight, a unification fight, or simply the fight the fans want to see. Without these optional fights, the biggest fights would never happen.