"Guess you thought that out very clearly except for the fact that Judaism is only from the mother."
Judaism may officially go through the female line. But the Y-chromosome goes through the male line. Thus if you want to use the Jewish matrilineal definition of Judaism a proper study should study the mitochondrial DNA, not the Y-chromosome. The mitochondrial DNA is passed through the female line only.
That a Jew had a Jewish mother is a given. If anything needed to be tested it was the paternal line.
There have been confirmatory studies on the mitochondrial chromosomes published in the magazines Science and Nature which came to the same conclusions. It is beyond debate at this point.