Look at the length of the stop, and it isn't the fur on top of his head, as much as it is the throat latch.......where the jawline comes into the neck. Can you send us an example of what you think would be a deep head, and a light head? If the muzzle matched the skull on this dog, the muzzle would be massive and out of proportion.
Here is another example of a head with no depth.
http://www.sheltiesonline.com/ad_archive_2007/rabbit_run_052607.html
Are you using him as an example of a good head?

