You're talking about exceptions, not rules. No one is arguing its impossible for USU to win. On any given Saturday anything could happen.
For every Appy State/Michigan there are 50+ examples of the better team from the better conference winning. If USU wins it will be the exception, the thread is about them acting as though it would be the rule.
michigan was a top 5 team favored by 40 points against an FCS team. Oklahoma was top 10.
Tennessee doesn't have more than a handful of players who have ever played in a bowl game. They're currently 6.5 point favorites at home against a mid-major team with 4 new OL, a QB and an RB coming back from an ACL injury, and an all new backfield on defense.
if USU wins, it won't be an upset like app state. maybe comparable to Boise-oklahoma. oklahoma was the favorite, had more talent on paper, and got beat by a team that they should have respected more. but app-mich is a bad comparison.