I think you can argue that the experiment wasn't representative of 'normal' coin flips.

On average, each flipper in that experiment flipped a coin over 7000 times, after that amount many people will have learned to flip in a comfortable way with less variance between physical action and force they use. I'd imagine that in that case the coin would more likely land with the same orientation.

I don't think this would be true if someone flipped without practice.