understand why SMU didn’t use their time out either.
Your explanation might’ve been correct, but don’t belittle somebody for wondering what was going on.
Regardless of whether SMU was using “sportsmanship“ and was conceding the game, another coach (Whittingham) could’ve easily pulled a “Yewt” and called their time out when they saw that BYU kneeled down with 18 seconds to go. That would’ve stopped the clock with 4th down coming up and causing BYU to punt with 18 seconds left.