Are you serious?
He kept turning so that only the back of his head was exposed.
It's a fucking shit rule anyway
Blind people are blind.
If you're facedown on the canvas and the only way you can protect yourself is turning your head so that your opponent hit you in the back of your head, the ref should stop the fight because I don't see that as an inteligent way to protect yourself.
I didn't see that fight but bear in mind that if the strike lands even partially on the side of the head it's technically legal