If it were a running back, sure... but you know any QB is going to make a beeline for the sidelines. It was obvious in watching the play.
It may have been obvious to you watching the play but go back to the photo you posted.
Quinn's NOT beelining for the sideline. He's turned upfield in the hash marks. He's definitely dropped his leading shoulder and turned his body to protect the ball. IF he was beelining for the sideline he would have been out of bounds already. Then perhaps warranting a late hit penalty. But no so with his footwork.
Without the shoulder drop and turn the tackle is made chest high with legs driving. The tackler's head is positioned on the front side of Quinn's chest if Quinn doesn't drop his shoulder.
A helmet hit is a penalty regardless of intent and you're only guessing at that. Your photo doesn't support the scenario you set.
If Crum had made the same tackle on Reggie Ball, we'd be screaming the helmet was incidental. But it'd still be a penalty.
Advantage KMac!