The wording “next” makes it unclear and seems to imply it is talking about the next common opponent after BYU and ISU, which would not include Kansas St. This would be an odd tie-breaker to use, but by the letter of the law seems to exclude the KSU win.
“The tied teams will be compared based on win percentage against the next highest-placed common opponent in the standings (based on the record in all games played within the conference) proceeding through the standings.”