My cat did more damage to me yesterday when he attacked my arm, gouged it in two spots and put a two inch scratch on my elbow! The scratch on my elbow was much more evident than any damage in that picture of GZ's head and it bled more. (I've got a semi-feral cat who regularly attacks me, but I love him anyway.)
Both times I've had my head bashed against something (by horses), the injury was low on my skull, under the big "bump" at the back of the head, above the nape of the neck. They certainly were not on the top of the head where the picture shows GZ bleeding. I have had cuts up in that area, from hitting my head when I didn't duck low enough or raised my head too soon when walking under a low branch or opening.
Just saying, so IMO, JMO, etc.