If the claim is that the majority of humans speak a language which includes huh? as a feature, then sure. But that doesn't seem very interesting scientifically...
By calling it a universal word, I guess I thought they were referring to the concept of linguistic universals [1], which are interesting since they might suggest something about the deeper way in which our brains work. To make a claim about linguistic universals like that I really think they should study more than 10 (31) languages.
According to this page [2], 44% of people speak an Indo-European language, and 96% speak a member of one of the top 10 language families. The remaining 4% includes 84 language families. I imagine there's a ton of variety there, and for understanding human language and cognition they all probably have just as much value as the larger language families.
Universal should mean that virtually every human in history used it. Just because something is pervasive in modern societies does not mean is a fundamental feature of human nature. Language is universal. Fear and anger are universal.
