So I am no expert but
He doesn't determine trajectory at the scene, just on the body.
Well how does he know what position the body is in at any given time? How can he even say it was an elevated position and NOT mean the person could be taller? The body could be on the ground, standing, bent over, etc. So trajectory in the body is one thing, but he can't give any opinion on where the shooter was, how tall they were because he has no idea how the victim was standing, bending, sitting, laying, etc.