I checked the "destroy my sample after analysis" checkbox. So the analysis is there but not the actual sample. Maybe this is somewhat better?
That's the only reassurance I have. It would be like illegally collected evidence. Sure, you may have some evidence (my DNA), but it's not admissible because you're not supposed to have had access to it.
Are there analogous rules around the DNA sent to 23andMe, would you have an enforceable opportunity to block uses of that, and would you even know when they're using it that way?
Honest and sincere question: why would you even use their service in the first place?