If you or I were pushed backwards, if we could not keep our footing, we would land on our butts, with hands or elbows by our side. It is the human instinct to elevate the head as we fall backwards. The only way he should have hit his head is if he was unconscious when he fell backwards. This was a flop that turned out badly for him.
my lovely (cough cough) mom shoved me backwards in the chest when I was about four and I cracked my head on the kitchen floor. She looked at me and said How does that feel? I had to pick myself up and go lie down — I knew she had no regard for me whatsoever. I will never forgive her. I don’t love her. But yes, if you get pushed backwards you definitely hit your head.