A good point, but not a foolproof one. There was significant contact back and forth, they aren't hermetically sealed groups.
I'd like to see the source though, Xinhua is only slightly more reliable than Debka.
Actually, they may as well have been. The families did not intermarry back then. Furthermore, the Askenasi were originally Khazars who converted to Judaism circa 1200 A.D. - no connection to Israel.