First, it's not much of a reaction to be traversed through your torso with a bullet, to raise your arm. But second, what's he talking about?
I don't know what Corbett is talking about, but there is no sign there that Connally has been hit. He's sitting up straight and not reacting at all. He definitely has not had a bullet traverse his chest, blow up his wrist, and penetrate his thigh.
And how does a guy whose wrist has been shattered continue to clutch a hat?
Z-236 is when there is clear visual evidence of Connally reacting to being shot.
Hey, Corbett. One of us lives in the real world. It ain't you.