BYU then either accepts and we have a better strength of schedule than FSU would provide, or they decline and therefore and any potential talk they have if they happen to go undefeated. Basically nip it in the bud so that they can't do like UCF did a few years ago claiming a title.
Look at BYU's schedule this year. I know it's not their fault that they don't have a homeboy (Swofford) like ND to let them in a Power 5 conference(ACC) and offer them a chance at a conference championship for just one year but I don't think BYU's own SOS is going to help anyone.