Rodgers does hold the ball a bit low when scrambling and sitting in the pocket, but he actually cheats a bit here and raises the ball as he locks onto a target, right before he throws it. It's kind of funny to watch him go through progressions as he raises the ball slightly when he's zeroing in on a receiver, then lowers it a bit as he scans for another target. When he's on the run, he takes a long wind up and avoids the quick release he normally tosses.
Brock has more of a Tim Tebow motion from what I can see. I know this isn't the best play to show his motion, but it's the first one I found with a slowed view and HD quality. You can see he's not under pressure, swings the ball low, and comes up over his head with a U shaped hand holding the ball from the underside. His hand is also pretty far from the rest of his body, which is probably due to his arm length and height, but it's not mechanically ideal for a passer. Anyways, I really do think there are fundamental issues with his delivery that could be improved, but I do think his slow throwing motion is part of the problem and also contributes to his inability to hit receivers in stride.