Think it over. All the children of Jewish women are Jewish. Jewish men have no impact on whether or not their kids are Jewish.
At the end of the day the figures cited counted men, and those men realistically need to marry Jewish women for their progeny to be Jewish. Same for the women, if they intermarry it’s of lower likelihood their progeny will live Jewishly and identify as Jewish.
Additionally, assimilation doesn’t have to be through intermarriage. If you have enough generations of people who don’t self-identify as Jewish, the fact that all of their ancestors are Jewish is irrelevant (especially since they can’t trace it, but mostly because they don’t care to)