Is the QB different? Sure. He's the star of the team. But that comes with another responsibility.
One of the differences is that QBs are in a better position to get hurt. That's why the second string QB is often the second most important player on the team.
Every player told he's in "rotation" knows he will have to become the better of the two players if he wants to extend his playing career. You either wait for an injury, or outplay him in practice. Not so different from the back-up QB.
When you leave the college, your team and your teammates the moment the depth chart is revealed, you literally believe you are better than this, and it's not a great message. A WR, RB, DB or god-forbid an interior lineman would be considered a huge primadonna if he bolted at the first depth chart.
And yeah, there's usually a father behind these decisions.
Maybe Tristan Gebbia is that special. We'll see.