Great piece from that Chargers article
In the excellent book 'Take Your Eye Off The Ball' by Pat Kirwan, he makes the point that, as much as a quarterback wants to step into his throw, most of the time that isn't possible. Instead, the QB will have to make do with the situation given to them - a compromised pocket - and have to throw it from all sorts of positions and angles. Dan Marino says that "if I worked out a QB for an NFL team, he'd have to show me 100 throws off his back foot."