"I felt like he kind of jumped a little bit, and that caused me to go lower," Jennings said. "I just have to tackle up high when I'm pressuring the quarterback." ...
I knew why we got the penalty, but the rule needs to encompass movement of the QB. If he's running or jumping backwards (as he was), then he isn't going to be injured by a low tackle.
The injury comes from a QB being hit while standing upright in the pocket or stepping forward into a throw. That was the situation that injured Tom Brady and so many others. This instance was evidence that a tackler can't always choose the position of his tackle. If the QB is moving backwards the rule shouldn't apply.