That was true in the past, but is irrelevant now that insurance companies can't refuse to insure you, or even charge you more for pre-existing conditions.
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.
My point was, no, insurance companies can't use the data, even if they had access to the it, which they won't.
No car breakdown insurance lets you take out a policy to cover the vehicle after it has already broken down...