I don’t think that is necessary. All the police need to do is send in a sample of the perp’s DNA and use any made up name for example John Doe Rapist.
Then the service will try to locate any one who is a relative — even if very distant. Then you have to do the detective work to find out if this person has any one who could be a valid suspect. The actual person does not need to put in DNA and they don’t have to ask for permission to search the data base.
After all, the true perp will very likely not be a user of the system, this method of tracking depends on a population of people who are interested in who may be related to them.
what you describe is horrifying.
these site should NOT be in the business of doing that unless served with a warrant for a specific person’s dna.