I think BYU is in no negotiations right now, full membership or football only is not on the table. He was asked, he answered that football only was not an option. That is it. The Big 12 hasn't made up their mind regarding any of this, expand/not expand, BYU/not BYU, football only/everything. There is no mind to change. When/if they create a plan to expand, then we will see.
He simply stated that RIGHT NOW football only was not an option to joining a P5 conference. Anything else is added conjecture and speculation.