I don't understand, the parent said nothing about Jews at all. Nonetheless, given the incidence among them, they also happen to be pioneers in prescreening for this very genetic defect.
Genetic testing can identify carriers, so if Tay-Sachs has been (mostly) 'vanquished' from the Ashkenazi community, it can be 'vanquished' completely.
https://www.nytimes.com/2003/02/18/science/using-genetic-tes...