I'm sorry but that sounds like an appeal to authority to me. The original author is basing his article on solid figures (which, granted, he may be interpreting incorrectly) whereas you are making an argument based on your intuition.

Do you have any data at all that directly tests the effect of headshots on organic search results? Extrapolating from other rich metadata decoration is invalid. Small changes in design can lead to big differences in user behavior. That's why we A/B test in the first place.