75 individuals seems like a small group to study. Were there any differences between Ashkenazi and Sephardic Jews? How about Yemeni Jews? They may not have had enough from each group to draw any firm conclusions. How about comparisons with the Samaritans or with Lebanese or Palestinian Christians--the trait may not be limited only to Jews.
I'm thinking the same thing.
Yep, none of the Israelites were named Jews until well after the split into Northern and Southern Kingdoms, about 922 BC.