Not true at all. If you know you are at higher risk thanks to your personal genetic test, you are more likely to buy yourself good insurance coverage.
1) More high risk customers buying the insurance concentrates the 'pool' of insured risks...
2) ...leading to more payouts
3) ...leading to higher insurance
4) ...leading to those without the risks opting to take cheaper, lower level coverage
5) ...leading to more concentrated risk in the pool of insured people in the good coverage
6) ...and back to step 2. The insurance fails, or becomes too high a cost to be worthwhile for anyone.