It isn't just the offense though that is getting in all those extra plays, it is the BYU defense as well. I dont know the number but recall reading somewhere that the defense played significantly more plays as well, thus equaling more collisions, more opportunities for serious injury, more opportunities for lingering injuries that limit a players effectiveness but dont keep them off the field, etc.

I dont disagree with you about UW and the quality of athlete they had, but I don't think they are mutually exclusive things either - UW did have very good athletes AND BYU (in my opinion) was impacted by gfgh with guys out or injured or slowed. (obligatory disclaimer all teams have that at end of year, my feelign is just BYU had it more)