Did any of us wonder why Matt Cohen was cast as John since he and JDM look only vaguely similar in the sense that if you gave their description to a police officer they might both turn up on the line-up. But, as I said, earlier, there I was looking at stills, and all of a sudden it hit me in the same way that Vogue spread did when they were organizing their models to mirror famous works of art.
Matt Cohen's body language is SOOOO similar to Sam's, from the hands in pockets, the slight head-tilt like he's trying to minimize his height, the furrowed brows, but otherwise expressionless face.
Unfortunately Lucy and I can find like 80 of a similar pose, but not with the same angle, I'm like, I KNOW I'VE SEEN SAM DO THIS IN THIS EXACT MANNER, DAMN IT. I WILL FIND IT. But here, for you...
And this with the hands high on the hips, but the shoulders still rolled under, NOT TO MENTION THE OUTFIT.
So my thought is that they cast him because they wanted to emphasize how similar John and Sam are (which is why Dean can work with both of them, but they can't work with each other), and he could convincingly immitate Jared's body language for Sam.