I still largely agree that it's worth keeping your DNA out of the hands of data brokers for several reasons, but as laws exist today that would not be legal.
It's reminiscent of some prepper wanting to exclusively horde USD. I just don’t see a doomsday scenario in which that matters compared to hording gold or some other store of value with more intrinsic value. It's behavior suggests a weird cherry-picking of what are likely correlated risks.
Most people in the US are insured through private companies. How would it be unconstitutional for those companies to refuse to insure or jack up prices for people who decline genetic testing?
It just seems strange to believe that this data would be both incredibly valuable to health insurers and that they would have no new ways to gather it outside relying on decade old data from now defunct companies. Modern insurance companies don't identify smokers by buying the old Marlboro Miles database, they make disclosing smoking a part of the application process.