I can’t say I have ever examined dressed birds that closely, but on the few occasions that I have noticed how immaculate a shot bird has been, there is usually a pellet hole in the neck.
The clue is often in how the bird collapses after the shot.
If it is hit in the head it will invariably stall abruptly and, upon hitting the ground, will often roll backwards over and over.
If it is hit in the neck, there is every chance the nerves connecting the spinal cord will have been severed, and it simply folds its wings and drops like a stone.
This is where the top performers hit their birds, and why it looks so impressive.