Comment by busterarm
The point isn't what they are doing with your data now, but that they retain your data and what might happen in the future. Someone with malicious designs on your DNA might buy Nebula tomorrow and there's nothing you can do about it.
Actually, the main reason I used Nebula was that they advertised a credible-to-me promise that you could download and permanently delete your data upon request. That was some years ago, so I don't know if I would trust them today. But that was their claim, and I have no reason to believe they didn't delete my data.