It's all about in structure and out of structure.
A playcall has a primary read based on the coverage or leverage of the defender, you then go through the progressions, which in most systems is linked to how many steps a QB drops. Once he's gone through these the ball should be out. That's structure.
After this point the playcall is broken and you're out of structure, the misconception is that if you can operate out of structure, you can't work within it. This is simply not the case, it just takes a special QB to excel in both areas, and if you can you're practically unstoppable.
[ Edited by 49erBigMac on Feb 5, 2021 at 2:30 PM ]