In the medieval period, Ashkenazim were the most well-traveled people in the world. It was hardly uncommon for Jewish couples to be comprised of a man and a woman who were born in communities located hundreds of miles away from one another at a time when most Christian Europeans married people who were born in a 20 mile radius of their own birthplace.
I'm not sure why this is being represented as an unexpected find.
Agreed. "The Wandering Jew" became almost a mythological label, they were driven away from towns and cities an a regular basis, laws were passed prohibiting them from participation in long lists of professions, and pogroms were enacted against them by numerous groups
If they now didn't have a spread of genetic diversity as a result, that would be the real surprise.
Although come to think of it, perhaps this article is a refutation of the Jewish insistence of genetic/racial purity?
Could the fact that the Jewish population was small and dispersed but connected in trade also be a factor? They had to search far for mates, increasing heterozygosity.